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window.clrtobot()
Erase from cursor to the end of the window: all lines below the cursor are deleted, and then the equivalent of clrtoeol() is performed. | python.library.curses#curses.window.clrtobot |
window.clrtoeol()
Erase from cursor to the end of the line. | python.library.curses#curses.window.clrtoeol |
window.cursyncup()
Update the current cursor position of all the ancestors of the window to reflect the current cursor position of the window. | python.library.curses#curses.window.cursyncup |
window.delch([y, x])
Delete any character at (y, x). | python.library.curses#curses.window.delch |
window.deleteln()
Delete the line under the cursor. All following lines are moved up by one line. | python.library.curses#curses.window.deleteln |
window.derwin(begin_y, begin_x)
window.derwin(nlines, ncols, begin_y, begin_x)
An abbreviation for “derive window”, derwin() is the same as calling subwin(), except that begin_y and begin_x are relative to the origin of the window, rather than relative to the entire screen. Return a window object for the derived window. | python.library.curses#curses.window.derwin |
window.echochar(ch[, attr])
Add character ch with attribute attr, and immediately call refresh() on the window. | python.library.curses#curses.window.echochar |
window.enclose(y, x)
Test whether the given pair of screen-relative character-cell coordinates are enclosed by the given window, returning True or False. It is useful for determining what subset of the screen windows enclose the location of a mouse event. | python.library.curses#curses.window.enclose |
window.encoding
Encoding used to encode method arguments (Unicode strings and characters). The encoding attribute is inherited from the parent window when a subwindow is created, for example with window.subwin(). By default, the locale encoding is used (see locale.getpreferredencoding()). New in version 3.3. | python.library.curses#curses.window.encoding |
window.erase()
Clear the window. | python.library.curses#curses.window.erase |
window.getbegyx()
Return a tuple (y, x) of co-ordinates of upper-left corner. | python.library.curses#curses.window.getbegyx |
window.getbkgd()
Return the given window’s current background character/attribute pair. | python.library.curses#curses.window.getbkgd |
window.getch([y, x])
Get a character. Note that the integer returned does not have to be in ASCII range: function keys, keypad keys and so on are represented by numbers higher than 255. In no-delay mode, return -1 if there is no input, otherwise wait until a key is pressed. | python.library.curses#curses.window.getch |
window.getkey([y, x])
Get a character, returning a string instead of an integer, as getch() does. Function keys, keypad keys and other special keys return a multibyte string containing the key name. In no-delay mode, raise an exception if there is no input. | python.library.curses#curses.window.getkey |
window.getmaxyx()
Return a tuple (y, x) of the height and width of the window. | python.library.curses#curses.window.getmaxyx |
window.getparyx()
Return the beginning coordinates of this window relative to its parent window as a tuple (y, x). Return (-1, -1) if this window has no parent. | python.library.curses#curses.window.getparyx |
window.getstr()
window.getstr(n)
window.getstr(y, x)
window.getstr(y, x, n)
Read a bytes object from the user, with primitive line editing capacity. | python.library.curses#curses.window.getstr |
window.getyx()
Return a tuple (y, x) of current cursor position relative to the window’s upper-left corner. | python.library.curses#curses.window.getyx |
window.get_wch([y, x])
Get a wide character. Return a character for most keys, or an integer for function keys, keypad keys, and other special keys. In no-delay mode, raise an exception if there is no input. New in version 3.3. | python.library.curses#curses.window.get_wch |
window.hline(ch, n)
window.hline(y, x, ch, n)
Display a horizontal line starting at (y, x) with length n consisting of the character ch. | python.library.curses#curses.window.hline |
window.idcok(flag)
If flag is False, curses no longer considers using the hardware insert/delete character feature of the terminal; if flag is True, use of character insertion and deletion is enabled. When curses is first initialized, use of character insert/delete is enabled by default. | python.library.curses#curses.window.idcok |
window.idlok(flag)
If flag is True, curses will try and use hardware line editing facilities. Otherwise, line insertion/deletion are disabled. | python.library.curses#curses.window.idlok |
window.immedok(flag)
If flag is True, any change in the window image automatically causes the window to be refreshed; you no longer have to call refresh() yourself. However, it may degrade performance considerably, due to repeated calls to wrefresh. This option is disabled by default. | python.library.curses#curses.window.immedok |
window.inch([y, x])
Return the character at the given position in the window. The bottom 8 bits are the character proper, and upper bits are the attributes. | python.library.curses#curses.window.inch |
window.insch(ch[, attr])
window.insch(y, x, ch[, attr])
Paint character ch at (y, x) with attributes attr, moving the line from position x right by one character. | python.library.curses#curses.window.insch |
window.insdelln(nlines)
Insert nlines lines into the specified window above the current line. The nlines bottom lines are lost. For negative nlines, delete nlines lines starting with the one under the cursor, and move the remaining lines up. The bottom nlines lines are cleared. The current cursor position remains the same. | python.library.curses#curses.window.insdelln |
window.insertln()
Insert a blank line under the cursor. All following lines are moved down by one line. | python.library.curses#curses.window.insertln |
window.insnstr(str, n[, attr])
window.insnstr(y, x, str, n[, attr])
Insert a character string (as many characters as will fit on the line) before the character under the cursor, up to n characters. If n is zero or negative, the entire string is inserted. All characters to the right of the cursor are shifted right, with the rightmost characters on the line being lost. The cursor position does not change (after moving to y, x, if specified). | python.library.curses#curses.window.insnstr |
window.insstr(str[, attr])
window.insstr(y, x, str[, attr])
Insert a character string (as many characters as will fit on the line) before the character under the cursor. All characters to the right of the cursor are shifted right, with the rightmost characters on the line being lost. The cursor position does not change (after moving to y, x, if specified). | python.library.curses#curses.window.insstr |
window.instr([n])
window.instr(y, x[, n])
Return a bytes object of characters, extracted from the window starting at the current cursor position, or at y, x if specified. Attributes are stripped from the characters. If n is specified, instr() returns a string at most n characters long (exclusive of the trailing NUL). | python.library.curses#curses.window.instr |
window.is_linetouched(line)
Return True if the specified line was modified since the last call to refresh(); otherwise return False. Raise a curses.error exception if line is not valid for the given window. | python.library.curses#curses.window.is_linetouched |
window.is_wintouched()
Return True if the specified window was modified since the last call to refresh(); otherwise return False. | python.library.curses#curses.window.is_wintouched |
window.keypad(flag)
If flag is True, escape sequences generated by some keys (keypad, function keys) will be interpreted by curses. If flag is False, escape sequences will be left as is in the input stream. | python.library.curses#curses.window.keypad |
window.leaveok(flag)
If flag is True, cursor is left where it is on update, instead of being at “cursor position.” This reduces cursor movement where possible. If possible the cursor will be made invisible. If flag is False, cursor will always be at “cursor position” after an update. | python.library.curses#curses.window.leaveok |
window.move(new_y, new_x)
Move cursor to (new_y, new_x). | python.library.curses#curses.window.move |
window.mvderwin(y, x)
Move the window inside its parent window. The screen-relative parameters of the window are not changed. This routine is used to display different parts of the parent window at the same physical position on the screen. | python.library.curses#curses.window.mvderwin |
window.mvwin(new_y, new_x)
Move the window so its upper-left corner is at (new_y, new_x). | python.library.curses#curses.window.mvwin |
window.nodelay(flag)
If flag is True, getch() will be non-blocking. | python.library.curses#curses.window.nodelay |
window.notimeout(flag)
If flag is True, escape sequences will not be timed out. If flag is False, after a few milliseconds, an escape sequence will not be interpreted, and will be left in the input stream as is. | python.library.curses#curses.window.notimeout |
window.noutrefresh()
Mark for refresh but wait. This function updates the data structure representing the desired state of the window, but does not force an update of the physical screen. To accomplish that, call doupdate(). | python.library.curses#curses.window.noutrefresh |
window.overlay(destwin[, sminrow, smincol, dminrow, dmincol, dmaxrow, dmaxcol])
Overlay the window on top of destwin. The windows need not be the same size, only the overlapping region is copied. This copy is non-destructive, which means that the current background character does not overwrite the old contents of destwin. To get fine-grained control over the copied region, the second form of overlay() can be used. sminrow and smincol are the upper-left coordinates of the source window, and the other variables mark a rectangle in the destination window. | python.library.curses#curses.window.overlay |
window.overwrite(destwin[, sminrow, smincol, dminrow, dmincol, dmaxrow, dmaxcol])
Overwrite the window on top of destwin. The windows need not be the same size, in which case only the overlapping region is copied. This copy is destructive, which means that the current background character overwrites the old contents of destwin. To get fine-grained control over the copied region, the second form of overwrite() can be used. sminrow and smincol are the upper-left coordinates of the source window, the other variables mark a rectangle in the destination window. | python.library.curses#curses.window.overwrite |
window.putwin(file)
Write all data associated with the window into the provided file object. This information can be later retrieved using the getwin() function. | python.library.curses#curses.window.putwin |
window.redrawln(beg, num)
Indicate that the num screen lines, starting at line beg, are corrupted and should be completely redrawn on the next refresh() call. | python.library.curses#curses.window.redrawln |
window.redrawwin()
Touch the entire window, causing it to be completely redrawn on the next refresh() call. | python.library.curses#curses.window.redrawwin |
window.refresh([pminrow, pmincol, sminrow, smincol, smaxrow, smaxcol])
Update the display immediately (sync actual screen with previous drawing/deleting methods). The 6 optional arguments can only be specified when the window is a pad created with newpad(). The additional parameters are needed to indicate what part of the pad and screen are involved. pminrow and pmincol specify the upper left-hand corner of the rectangle to be displayed in the pad. sminrow, smincol, smaxrow, and smaxcol specify the edges of the rectangle to be displayed on the screen. The lower right-hand corner of the rectangle to be displayed in the pad is calculated from the screen coordinates, since the rectangles must be the same size. Both rectangles must be entirely contained within their respective structures. Negative values of pminrow, pmincol, sminrow, or smincol are treated as if they were zero. | python.library.curses#curses.window.refresh |
window.resize(nlines, ncols)
Reallocate storage for a curses window to adjust its dimensions to the specified values. If either dimension is larger than the current values, the window’s data is filled with blanks that have the current background rendition (as set by bkgdset()) merged into them. | python.library.curses#curses.window.resize |
window.scroll([lines=1])
Scroll the screen or scrolling region upward by lines lines. | python.library.curses#curses.window.scroll |
window.scrollok(flag)
Control what happens when the cursor of a window is moved off the edge of the window or scrolling region, either as a result of a newline action on the bottom line, or typing the last character of the last line. If flag is False, the cursor is left on the bottom line. If flag is True, the window is scrolled up one line. Note that in order to get the physical scrolling effect on the terminal, it is also necessary to call idlok(). | python.library.curses#curses.window.scrollok |
window.setscrreg(top, bottom)
Set the scrolling region from line top to line bottom. All scrolling actions will take place in this region. | python.library.curses#curses.window.setscrreg |
window.standend()
Turn off the standout attribute. On some terminals this has the side effect of turning off all attributes. | python.library.curses#curses.window.standend |
window.standout()
Turn on attribute A_STANDOUT. | python.library.curses#curses.window.standout |
window.subpad(begin_y, begin_x)
window.subpad(nlines, ncols, begin_y, begin_x)
Return a sub-window, whose upper-left corner is at (begin_y, begin_x), and whose width/height is ncols/nlines. | python.library.curses#curses.window.subpad |
window.subwin(begin_y, begin_x)
window.subwin(nlines, ncols, begin_y, begin_x)
Return a sub-window, whose upper-left corner is at (begin_y, begin_x), and whose width/height is ncols/nlines. By default, the sub-window will extend from the specified position to the lower right corner of the window. | python.library.curses#curses.window.subwin |
window.syncdown()
Touch each location in the window that has been touched in any of its ancestor windows. This routine is called by refresh(), so it should almost never be necessary to call it manually. | python.library.curses#curses.window.syncdown |
window.syncok(flag)
If flag is True, then syncup() is called automatically whenever there is a change in the window. | python.library.curses#curses.window.syncok |
window.syncup()
Touch all locations in ancestors of the window that have been changed in the window. | python.library.curses#curses.window.syncup |
window.timeout(delay)
Set blocking or non-blocking read behavior for the window. If delay is negative, blocking read is used (which will wait indefinitely for input). If delay is zero, then non-blocking read is used, and getch() will return -1 if no input is waiting. If delay is positive, then getch() will block for delay milliseconds, and return -1 if there is still no input at the end of that time. | python.library.curses#curses.window.timeout |
window.touchline(start, count[, changed])
Pretend count lines have been changed, starting with line start. If changed is supplied, it specifies whether the affected lines are marked as having been changed (changed=True) or unchanged (changed=False). | python.library.curses#curses.window.touchline |
window.touchwin()
Pretend the whole window has been changed, for purposes of drawing optimizations. | python.library.curses#curses.window.touchwin |
window.untouchwin()
Mark all lines in the window as unchanged since the last call to refresh(). | python.library.curses#curses.window.untouchwin |
window.vline(ch, n)
window.vline(y, x, ch, n)
Display a vertical line starting at (y, x) with length n consisting of the character ch. | python.library.curses#curses.window.vline |
curses.wrapper(func, /, *args, **kwargs)
Initialize curses and call another callable object, func, which should be the rest of your curses-using application. If the application raises an exception, this function will restore the terminal to a sane state before re-raising the exception and generating a traceback. The callable object func is then passed the main window ‘stdscr’ as its first argument, followed by any other arguments passed to wrapper(). Before calling func, wrapper() turns on cbreak mode, turns off echo, enables the terminal keypad, and initializes colors if the terminal has color support. On exit (whether normally or by exception) it restores cooked mode, turns on echo, and disables the terminal keypad. | python.library.curses#curses.wrapper |
dataclasses — Data Classes Source code: Lib/dataclasses.py This module provides a decorator and functions for automatically adding generated special methods such as __init__() and __repr__() to user-defined classes. It was originally described in PEP 557. The member variables to use in these generated methods are defined using PEP 526 type annotations. For example this code: from dataclasses import dataclass
@dataclass
class InventoryItem:
"""Class for keeping track of an item in inventory."""
name: str
unit_price: float
quantity_on_hand: int = 0
def total_cost(self) -> float:
return self.unit_price * self.quantity_on_hand
Will add, among other things, a __init__() that looks like: def __init__(self, name: str, unit_price: float, quantity_on_hand: int=0):
self.name = name
self.unit_price = unit_price
self.quantity_on_hand = quantity_on_hand
Note that this method is automatically added to the class: it is not directly specified in the InventoryItem definition shown above. New in version 3.7. Module-level decorators, classes, and functions
@dataclasses.dataclass(*, init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False)
This function is a decorator that is used to add generated special methods to classes, as described below. The dataclass() decorator examines the class to find fields. A field is defined as class variable that has a type annotation. With two exceptions described below, nothing in dataclass() examines the type specified in the variable annotation. The order of the fields in all of the generated methods is the order in which they appear in the class definition. The dataclass() decorator will add various “dunder” methods to the class, described below. If any of the added methods already exist on the class, the behavior depends on the parameter, as documented below. The decorator returns the same class that is called on; no new class is created. If dataclass() is used just as a simple decorator with no parameters, it acts as if it has the default values documented in this signature. That is, these three uses of dataclass() are equivalent: @dataclass
class C:
...
@dataclass()
class C:
...
@dataclass(init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False)
class C:
...
The parameters to dataclass() are:
init: If true (the default), a __init__() method will be generated. If the class already defines __init__(), this parameter is ignored.
repr: If true (the default), a __repr__() method will be generated. The generated repr string will have the class name and the name and repr of each field, in the order they are defined in the class. Fields that are marked as being excluded from the repr are not included. For example: InventoryItem(name='widget', unit_price=3.0, quantity_on_hand=10). If the class already defines __repr__(), this parameter is ignored.
eq: If true (the default), an __eq__() method will be generated. This method compares the class as if it were a tuple of its fields, in order. Both instances in the comparison must be of the identical type. If the class already defines __eq__(), this parameter is ignored.
order: If true (the default is False), __lt__(), __le__(), __gt__(), and __ge__() methods will be generated. These compare the class as if it were a tuple of its fields, in order. Both instances in the comparison must be of the identical type. If order is true and eq is false, a ValueError is raised. If the class already defines any of __lt__(), __le__(), __gt__(), or __ge__(), then TypeError is raised.
unsafe_hash: If False (the default), a __hash__() method is generated according to how eq and frozen are set. __hash__() is used by built-in hash(), and when objects are added to hashed collections such as dictionaries and sets. Having a __hash__() implies that instances of the class are immutable. Mutability is a complicated property that depends on the programmer’s intent, the existence and behavior of __eq__(), and the values of the eq and frozen flags in the dataclass() decorator. By default, dataclass() will not implicitly add a __hash__() method unless it is safe to do so. Neither will it add or change an existing explicitly defined __hash__() method. Setting the class attribute __hash__ = None has a specific meaning to Python, as described in the __hash__() documentation. If __hash__() is not explicitly defined, or if it is set to None, then dataclass() may add an implicit __hash__() method. Although not recommended, you can force dataclass() to create a __hash__() method with unsafe_hash=True. This might be the case if your class is logically immutable but can nonetheless be mutated. This is a specialized use case and should be considered carefully. Here are the rules governing implicit creation of a __hash__() method. Note that you cannot both have an explicit __hash__() method in your dataclass and set unsafe_hash=True; this will result in a TypeError. If eq and frozen are both true, by default dataclass() will generate a __hash__() method for you. If eq is true and frozen is false, __hash__() will be set to None, marking it unhashable (which it is, since it is mutable). If eq is false, __hash__() will be left untouched meaning the __hash__() method of the superclass will be used (if the superclass is object, this means it will fall back to id-based hashing).
frozen: If true (the default is False), assigning to fields will generate an exception. This emulates read-only frozen instances. If __setattr__() or __delattr__() is defined in the class, then TypeError is raised. See the discussion below. fields may optionally specify a default value, using normal Python syntax: @dataclass
class C:
a: int # 'a' has no default value
b: int = 0 # assign a default value for 'b'
In this example, both a and b will be included in the added __init__() method, which will be defined as: def __init__(self, a: int, b: int = 0):
TypeError will be raised if a field without a default value follows a field with a default value. This is true either when this occurs in a single class, or as a result of class inheritance.
dataclasses.field(*, default=MISSING, default_factory=MISSING, repr=True, hash=None, init=True, compare=True, metadata=None)
For common and simple use cases, no other functionality is required. There are, however, some dataclass features that require additional per-field information. To satisfy this need for additional information, you can replace the default field value with a call to the provided field() function. For example: @dataclass
class C:
mylist: list[int] = field(default_factory=list)
c = C()
c.mylist += [1, 2, 3]
As shown above, the MISSING value is a sentinel object used to detect if the default and default_factory parameters are provided. This sentinel is used because None is a valid value for default. No code should directly use the MISSING value. The parameters to field() are:
default: If provided, this will be the default value for this field. This is needed because the field() call itself replaces the normal position of the default value.
default_factory: If provided, it must be a zero-argument callable that will be called when a default value is needed for this field. Among other purposes, this can be used to specify fields with mutable default values, as discussed below. It is an error to specify both default and default_factory.
init: If true (the default), this field is included as a parameter to the generated __init__() method.
repr: If true (the default), this field is included in the string returned by the generated __repr__() method.
compare: If true (the default), this field is included in the generated equality and comparison methods (__eq__(), __gt__(), et al.).
hash: This can be a bool or None. If true, this field is included in the generated __hash__() method. If None (the default), use the value of compare: this would normally be the expected behavior. A field should be considered in the hash if it’s used for comparisons. Setting this value to anything other than None is discouraged. One possible reason to set hash=False but compare=True would be if a field is expensive to compute a hash value for, that field is needed for equality testing, and there are other fields that contribute to the type’s hash value. Even if a field is excluded from the hash, it will still be used for comparisons.
metadata: This can be a mapping or None. None is treated as an empty dict. This value is wrapped in MappingProxyType() to make it read-only, and exposed on the Field object. It is not used at all by Data Classes, and is provided as a third-party extension mechanism. Multiple third-parties can each have their own key, to use as a namespace in the metadata. If the default value of a field is specified by a call to field(), then the class attribute for this field will be replaced by the specified default value. If no default is provided, then the class attribute will be deleted. The intent is that after the dataclass() decorator runs, the class attributes will all contain the default values for the fields, just as if the default value itself were specified. For example, after: @dataclass
class C:
x: int
y: int = field(repr=False)
z: int = field(repr=False, default=10)
t: int = 20
The class attribute C.z will be 10, the class attribute C.t will be 20, and the class attributes C.x and C.y will not be set.
class dataclasses.Field
Field objects describe each defined field. These objects are created internally, and are returned by the fields() module-level method (see below). Users should never instantiate a Field object directly. Its documented attributes are:
name: The name of the field.
type: The type of the field.
default, default_factory, init, repr, hash, compare, and metadata have the identical meaning and values as they do in the field() declaration. Other attributes may exist, but they are private and must not be inspected or relied on.
dataclasses.fields(class_or_instance)
Returns a tuple of Field objects that define the fields for this dataclass. Accepts either a dataclass, or an instance of a dataclass. Raises TypeError if not passed a dataclass or instance of one. Does not return pseudo-fields which are ClassVar or InitVar.
dataclasses.asdict(instance, *, dict_factory=dict)
Converts the dataclass instance to a dict (by using the factory function dict_factory). Each dataclass is converted to a dict of its fields, as name: value pairs. dataclasses, dicts, lists, and tuples are recursed into. For example: @dataclass
class Point:
x: int
y: int
@dataclass
class C:
mylist: list[Point]
p = Point(10, 20)
assert asdict(p) == {'x': 10, 'y': 20}
c = C([Point(0, 0), Point(10, 4)])
assert asdict(c) == {'mylist': [{'x': 0, 'y': 0}, {'x': 10, 'y': 4}]}
Raises TypeError if instance is not a dataclass instance.
dataclasses.astuple(instance, *, tuple_factory=tuple)
Converts the dataclass instance to a tuple (by using the factory function tuple_factory). Each dataclass is converted to a tuple of its field values. dataclasses, dicts, lists, and tuples are recursed into. Continuing from the previous example: assert astuple(p) == (10, 20)
assert astuple(c) == ([(0, 0), (10, 4)],)
Raises TypeError if instance is not a dataclass instance.
dataclasses.make_dataclass(cls_name, fields, *, bases=(), namespace=None, init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False)
Creates a new dataclass with name cls_name, fields as defined in fields, base classes as given in bases, and initialized with a namespace as given in namespace. fields is an iterable whose elements are each either name, (name, type), or (name, type, Field). If just name is supplied, typing.Any is used for type. The values of init, repr, eq, order, unsafe_hash, and frozen have the same meaning as they do in dataclass(). This function is not strictly required, because any Python mechanism for creating a new class with __annotations__ can then apply the dataclass() function to convert that class to a dataclass. This function is provided as a convenience. For example: C = make_dataclass('C',
[('x', int),
'y',
('z', int, field(default=5))],
namespace={'add_one': lambda self: self.x + 1})
Is equivalent to: @dataclass
class C:
x: int
y: 'typing.Any'
z: int = 5
def add_one(self):
return self.x + 1
dataclasses.replace(instance, /, **changes)
Creates a new object of the same type of instance, replacing fields with values from changes. If instance is not a Data Class, raises TypeError. If values in changes do not specify fields, raises TypeError. The newly returned object is created by calling the __init__() method of the dataclass. This ensures that __post_init__(), if present, is also called. Init-only variables without default values, if any exist, must be specified on the call to replace() so that they can be passed to __init__() and __post_init__(). It is an error for changes to contain any fields that are defined as having init=False. A ValueError will be raised in this case. Be forewarned about how init=False fields work during a call to replace(). They are not copied from the source object, but rather are initialized in __post_init__(), if they’re initialized at all. It is expected that init=False fields will be rarely and judiciously used. If they are used, it might be wise to have alternate class constructors, or perhaps a custom replace() (or similarly named) method which handles instance copying.
dataclasses.is_dataclass(class_or_instance)
Return True if its parameter is a dataclass or an instance of one, otherwise return False. If you need to know if a class is an instance of a dataclass (and not a dataclass itself), then add a further check for not
isinstance(obj, type): def is_dataclass_instance(obj):
return is_dataclass(obj) and not isinstance(obj, type)
Post-init processing The generated __init__() code will call a method named __post_init__(), if __post_init__() is defined on the class. It will normally be called as self.__post_init__(). However, if any InitVar fields are defined, they will also be passed to __post_init__() in the order they were defined in the class. If no __init__() method is generated, then __post_init__() will not automatically be called. Among other uses, this allows for initializing field values that depend on one or more other fields. For example: @dataclass
class C:
a: float
b: float
c: float = field(init=False)
def __post_init__(self):
self.c = self.a + self.b
See the section below on init-only variables for ways to pass parameters to __post_init__(). Also see the warning about how replace() handles init=False fields. Class variables One of two places where dataclass() actually inspects the type of a field is to determine if a field is a class variable as defined in PEP 526. It does this by checking if the type of the field is typing.ClassVar. If a field is a ClassVar, it is excluded from consideration as a field and is ignored by the dataclass mechanisms. Such ClassVar pseudo-fields are not returned by the module-level fields() function. Init-only variables The other place where dataclass() inspects a type annotation is to determine if a field is an init-only variable. It does this by seeing if the type of a field is of type dataclasses.InitVar. If a field is an InitVar, it is considered a pseudo-field called an init-only field. As it is not a true field, it is not returned by the module-level fields() function. Init-only fields are added as parameters to the generated __init__() method, and are passed to the optional __post_init__() method. They are not otherwise used by dataclasses. For example, suppose a field will be initialized from a database, if a value is not provided when creating the class: @dataclass
class C:
i: int
j: int = None
database: InitVar[DatabaseType] = None
def __post_init__(self, database):
if self.j is None and database is not None:
self.j = database.lookup('j')
c = C(10, database=my_database)
In this case, fields() will return Field objects for i and j, but not for database. Frozen instances It is not possible to create truly immutable Python objects. However, by passing frozen=True to the dataclass() decorator you can emulate immutability. In that case, dataclasses will add __setattr__() and __delattr__() methods to the class. These methods will raise a FrozenInstanceError when invoked. There is a tiny performance penalty when using frozen=True: __init__() cannot use simple assignment to initialize fields, and must use object.__setattr__(). Inheritance When the dataclass is being created by the dataclass() decorator, it looks through all of the class’s base classes in reverse MRO (that is, starting at object) and, for each dataclass that it finds, adds the fields from that base class to an ordered mapping of fields. After all of the base class fields are added, it adds its own fields to the ordered mapping. All of the generated methods will use this combined, calculated ordered mapping of fields. Because the fields are in insertion order, derived classes override base classes. An example: @dataclass
class Base:
x: Any = 15.0
y: int = 0
@dataclass
class C(Base):
z: int = 10
x: int = 15
The final list of fields is, in order, x, y, z. The final type of x is int, as specified in class C. The generated __init__() method for C will look like: def __init__(self, x: int = 15, y: int = 0, z: int = 10):
Default factory functions If a field() specifies a default_factory, it is called with zero arguments when a default value for the field is needed. For example, to create a new instance of a list, use: mylist: list = field(default_factory=list)
If a field is excluded from __init__() (using init=False) and the field also specifies default_factory, then the default factory function will always be called from the generated __init__() function. This happens because there is no other way to give the field an initial value. Mutable default values Python stores default member variable values in class attributes. Consider this example, not using dataclasses: class C:
x = []
def add(self, element):
self.x.append(element)
o1 = C()
o2 = C()
o1.add(1)
o2.add(2)
assert o1.x == [1, 2]
assert o1.x is o2.x
Note that the two instances of class C share the same class variable x, as expected. Using dataclasses, if this code was valid: @dataclass
class D:
x: List = []
def add(self, element):
self.x += element
it would generate code similar to: class D:
x = []
def __init__(self, x=x):
self.x = x
def add(self, element):
self.x += element
assert D().x is D().x
This has the same issue as the original example using class C. That is, two instances of class D that do not specify a value for x when creating a class instance will share the same copy of x. Because dataclasses just use normal Python class creation they also share this behavior. There is no general way for Data Classes to detect this condition. Instead, dataclasses will raise a TypeError if it detects a default parameter of type list, dict, or set. This is a partial solution, but it does protect against many common errors. Using default factory functions is a way to create new instances of mutable types as default values for fields: @dataclass
class D:
x: list = field(default_factory=list)
assert D().x is not D().x
Exceptions
exception dataclasses.FrozenInstanceError
Raised when an implicitly defined __setattr__() or __delattr__() is called on a dataclass which was defined with frozen=True. It is a subclass of AttributeError. | python.library.dataclasses |
dataclasses.asdict(instance, *, dict_factory=dict)
Converts the dataclass instance to a dict (by using the factory function dict_factory). Each dataclass is converted to a dict of its fields, as name: value pairs. dataclasses, dicts, lists, and tuples are recursed into. For example: @dataclass
class Point:
x: int
y: int
@dataclass
class C:
mylist: list[Point]
p = Point(10, 20)
assert asdict(p) == {'x': 10, 'y': 20}
c = C([Point(0, 0), Point(10, 4)])
assert asdict(c) == {'mylist': [{'x': 0, 'y': 0}, {'x': 10, 'y': 4}]}
Raises TypeError if instance is not a dataclass instance. | python.library.dataclasses#dataclasses.asdict |
dataclasses.astuple(instance, *, tuple_factory=tuple)
Converts the dataclass instance to a tuple (by using the factory function tuple_factory). Each dataclass is converted to a tuple of its field values. dataclasses, dicts, lists, and tuples are recursed into. Continuing from the previous example: assert astuple(p) == (10, 20)
assert astuple(c) == ([(0, 0), (10, 4)],)
Raises TypeError if instance is not a dataclass instance. | python.library.dataclasses#dataclasses.astuple |
@dataclasses.dataclass(*, init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False)
This function is a decorator that is used to add generated special methods to classes, as described below. The dataclass() decorator examines the class to find fields. A field is defined as class variable that has a type annotation. With two exceptions described below, nothing in dataclass() examines the type specified in the variable annotation. The order of the fields in all of the generated methods is the order in which they appear in the class definition. The dataclass() decorator will add various “dunder” methods to the class, described below. If any of the added methods already exist on the class, the behavior depends on the parameter, as documented below. The decorator returns the same class that is called on; no new class is created. If dataclass() is used just as a simple decorator with no parameters, it acts as if it has the default values documented in this signature. That is, these three uses of dataclass() are equivalent: @dataclass
class C:
...
@dataclass()
class C:
...
@dataclass(init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False)
class C:
...
The parameters to dataclass() are:
init: If true (the default), a __init__() method will be generated. If the class already defines __init__(), this parameter is ignored.
repr: If true (the default), a __repr__() method will be generated. The generated repr string will have the class name and the name and repr of each field, in the order they are defined in the class. Fields that are marked as being excluded from the repr are not included. For example: InventoryItem(name='widget', unit_price=3.0, quantity_on_hand=10). If the class already defines __repr__(), this parameter is ignored.
eq: If true (the default), an __eq__() method will be generated. This method compares the class as if it were a tuple of its fields, in order. Both instances in the comparison must be of the identical type. If the class already defines __eq__(), this parameter is ignored.
order: If true (the default is False), __lt__(), __le__(), __gt__(), and __ge__() methods will be generated. These compare the class as if it were a tuple of its fields, in order. Both instances in the comparison must be of the identical type. If order is true and eq is false, a ValueError is raised. If the class already defines any of __lt__(), __le__(), __gt__(), or __ge__(), then TypeError is raised.
unsafe_hash: If False (the default), a __hash__() method is generated according to how eq and frozen are set. __hash__() is used by built-in hash(), and when objects are added to hashed collections such as dictionaries and sets. Having a __hash__() implies that instances of the class are immutable. Mutability is a complicated property that depends on the programmer’s intent, the existence and behavior of __eq__(), and the values of the eq and frozen flags in the dataclass() decorator. By default, dataclass() will not implicitly add a __hash__() method unless it is safe to do so. Neither will it add or change an existing explicitly defined __hash__() method. Setting the class attribute __hash__ = None has a specific meaning to Python, as described in the __hash__() documentation. If __hash__() is not explicitly defined, or if it is set to None, then dataclass() may add an implicit __hash__() method. Although not recommended, you can force dataclass() to create a __hash__() method with unsafe_hash=True. This might be the case if your class is logically immutable but can nonetheless be mutated. This is a specialized use case and should be considered carefully. Here are the rules governing implicit creation of a __hash__() method. Note that you cannot both have an explicit __hash__() method in your dataclass and set unsafe_hash=True; this will result in a TypeError. If eq and frozen are both true, by default dataclass() will generate a __hash__() method for you. If eq is true and frozen is false, __hash__() will be set to None, marking it unhashable (which it is, since it is mutable). If eq is false, __hash__() will be left untouched meaning the __hash__() method of the superclass will be used (if the superclass is object, this means it will fall back to id-based hashing).
frozen: If true (the default is False), assigning to fields will generate an exception. This emulates read-only frozen instances. If __setattr__() or __delattr__() is defined in the class, then TypeError is raised. See the discussion below. fields may optionally specify a default value, using normal Python syntax: @dataclass
class C:
a: int # 'a' has no default value
b: int = 0 # assign a default value for 'b'
In this example, both a and b will be included in the added __init__() method, which will be defined as: def __init__(self, a: int, b: int = 0):
TypeError will be raised if a field without a default value follows a field with a default value. This is true either when this occurs in a single class, or as a result of class inheritance. | python.library.dataclasses#dataclasses.dataclass |
class dataclasses.Field
Field objects describe each defined field. These objects are created internally, and are returned by the fields() module-level method (see below). Users should never instantiate a Field object directly. Its documented attributes are:
name: The name of the field.
type: The type of the field.
default, default_factory, init, repr, hash, compare, and metadata have the identical meaning and values as they do in the field() declaration. Other attributes may exist, but they are private and must not be inspected or relied on. | python.library.dataclasses#dataclasses.Field |
dataclasses.field(*, default=MISSING, default_factory=MISSING, repr=True, hash=None, init=True, compare=True, metadata=None)
For common and simple use cases, no other functionality is required. There are, however, some dataclass features that require additional per-field information. To satisfy this need for additional information, you can replace the default field value with a call to the provided field() function. For example: @dataclass
class C:
mylist: list[int] = field(default_factory=list)
c = C()
c.mylist += [1, 2, 3]
As shown above, the MISSING value is a sentinel object used to detect if the default and default_factory parameters are provided. This sentinel is used because None is a valid value for default. No code should directly use the MISSING value. The parameters to field() are:
default: If provided, this will be the default value for this field. This is needed because the field() call itself replaces the normal position of the default value.
default_factory: If provided, it must be a zero-argument callable that will be called when a default value is needed for this field. Among other purposes, this can be used to specify fields with mutable default values, as discussed below. It is an error to specify both default and default_factory.
init: If true (the default), this field is included as a parameter to the generated __init__() method.
repr: If true (the default), this field is included in the string returned by the generated __repr__() method.
compare: If true (the default), this field is included in the generated equality and comparison methods (__eq__(), __gt__(), et al.).
hash: This can be a bool or None. If true, this field is included in the generated __hash__() method. If None (the default), use the value of compare: this would normally be the expected behavior. A field should be considered in the hash if it’s used for comparisons. Setting this value to anything other than None is discouraged. One possible reason to set hash=False but compare=True would be if a field is expensive to compute a hash value for, that field is needed for equality testing, and there are other fields that contribute to the type’s hash value. Even if a field is excluded from the hash, it will still be used for comparisons.
metadata: This can be a mapping or None. None is treated as an empty dict. This value is wrapped in MappingProxyType() to make it read-only, and exposed on the Field object. It is not used at all by Data Classes, and is provided as a third-party extension mechanism. Multiple third-parties can each have their own key, to use as a namespace in the metadata. If the default value of a field is specified by a call to field(), then the class attribute for this field will be replaced by the specified default value. If no default is provided, then the class attribute will be deleted. The intent is that after the dataclass() decorator runs, the class attributes will all contain the default values for the fields, just as if the default value itself were specified. For example, after: @dataclass
class C:
x: int
y: int = field(repr=False)
z: int = field(repr=False, default=10)
t: int = 20
The class attribute C.z will be 10, the class attribute C.t will be 20, and the class attributes C.x and C.y will not be set. | python.library.dataclasses#dataclasses.field |
dataclasses.fields(class_or_instance)
Returns a tuple of Field objects that define the fields for this dataclass. Accepts either a dataclass, or an instance of a dataclass. Raises TypeError if not passed a dataclass or instance of one. Does not return pseudo-fields which are ClassVar or InitVar. | python.library.dataclasses#dataclasses.fields |
exception dataclasses.FrozenInstanceError
Raised when an implicitly defined __setattr__() or __delattr__() is called on a dataclass which was defined with frozen=True. It is a subclass of AttributeError. | python.library.dataclasses#dataclasses.FrozenInstanceError |
dataclasses.is_dataclass(class_or_instance)
Return True if its parameter is a dataclass or an instance of one, otherwise return False. If you need to know if a class is an instance of a dataclass (and not a dataclass itself), then add a further check for not
isinstance(obj, type): def is_dataclass_instance(obj):
return is_dataclass(obj) and not isinstance(obj, type) | python.library.dataclasses#dataclasses.is_dataclass |
dataclasses.make_dataclass(cls_name, fields, *, bases=(), namespace=None, init=True, repr=True, eq=True, order=False, unsafe_hash=False, frozen=False)
Creates a new dataclass with name cls_name, fields as defined in fields, base classes as given in bases, and initialized with a namespace as given in namespace. fields is an iterable whose elements are each either name, (name, type), or (name, type, Field). If just name is supplied, typing.Any is used for type. The values of init, repr, eq, order, unsafe_hash, and frozen have the same meaning as they do in dataclass(). This function is not strictly required, because any Python mechanism for creating a new class with __annotations__ can then apply the dataclass() function to convert that class to a dataclass. This function is provided as a convenience. For example: C = make_dataclass('C',
[('x', int),
'y',
('z', int, field(default=5))],
namespace={'add_one': lambda self: self.x + 1})
Is equivalent to: @dataclass
class C:
x: int
y: 'typing.Any'
z: int = 5
def add_one(self):
return self.x + 1 | python.library.dataclasses#dataclasses.make_dataclass |
dataclasses.replace(instance, /, **changes)
Creates a new object of the same type of instance, replacing fields with values from changes. If instance is not a Data Class, raises TypeError. If values in changes do not specify fields, raises TypeError. The newly returned object is created by calling the __init__() method of the dataclass. This ensures that __post_init__(), if present, is also called. Init-only variables without default values, if any exist, must be specified on the call to replace() so that they can be passed to __init__() and __post_init__(). It is an error for changes to contain any fields that are defined as having init=False. A ValueError will be raised in this case. Be forewarned about how init=False fields work during a call to replace(). They are not copied from the source object, but rather are initialized in __post_init__(), if they’re initialized at all. It is expected that init=False fields will be rarely and judiciously used. If they are used, it might be wise to have alternate class constructors, or perhaps a custom replace() (or similarly named) method which handles instance copying. | python.library.dataclasses#dataclasses.replace |
datetime — Basic date and time types Source code: Lib/datetime.py The datetime module supplies classes for manipulating dates and times. While date and time arithmetic is supported, the focus of the implementation is on efficient attribute extraction for output formatting and manipulation. See also
Module calendar
General calendar related functions.
Module time
Time access and conversions. Package dateutil
Third-party library with expanded time zone and parsing support. Aware and Naive Objects Date and time objects may be categorized as “aware” or “naive” depending on whether or not they include timezone information. With sufficient knowledge of applicable algorithmic and political time adjustments, such as time zone and daylight saving time information, an aware object can locate itself relative to other aware objects. An aware object represents a specific moment in time that is not open to interpretation. 1 A naive object does not contain enough information to unambiguously locate itself relative to other date/time objects. Whether a naive object represents Coordinated Universal Time (UTC), local time, or time in some other timezone is purely up to the program, just like it is up to the program whether a particular number represents metres, miles, or mass. Naive objects are easy to understand and to work with, at the cost of ignoring some aspects of reality. For applications requiring aware objects, datetime and time objects have an optional time zone information attribute, tzinfo, that can be set to an instance of a subclass of the abstract tzinfo class. These tzinfo objects capture information about the offset from UTC time, the time zone name, and whether daylight saving time is in effect. Only one concrete tzinfo class, the timezone class, is supplied by the datetime module. The timezone class can represent simple timezones with fixed offsets from UTC, such as UTC itself or North American EST and EDT timezones. Supporting timezones at deeper levels of detail is up to the application. The rules for time adjustment across the world are more political than rational, change frequently, and there is no standard suitable for every application aside from UTC. Constants The datetime module exports the following constants:
datetime.MINYEAR
The smallest year number allowed in a date or datetime object. MINYEAR is 1.
datetime.MAXYEAR
The largest year number allowed in a date or datetime object. MAXYEAR is 9999.
Available Types
class datetime.date
An idealized naive date, assuming the current Gregorian calendar always was, and always will be, in effect. Attributes: year, month, and day.
class datetime.time
An idealized time, independent of any particular day, assuming that every day has exactly 24*60*60 seconds. (There is no notion of “leap seconds” here.) Attributes: hour, minute, second, microsecond, and tzinfo.
class datetime.datetime
A combination of a date and a time. Attributes: year, month, day, hour, minute, second, microsecond, and tzinfo.
class datetime.timedelta
A duration expressing the difference between two date, time, or datetime instances to microsecond resolution.
class datetime.tzinfo
An abstract base class for time zone information objects. These are used by the datetime and time classes to provide a customizable notion of time adjustment (for example, to account for time zone and/or daylight saving time).
class datetime.timezone
A class that implements the tzinfo abstract base class as a fixed offset from the UTC. New in version 3.2.
Objects of these types are immutable. Subclass relationships: object
timedelta
tzinfo
timezone
time
date
datetime
Common Properties The date, datetime, time, and timezone types share these common features: Objects of these types are immutable. Objects of these types are hashable, meaning that they can be used as dictionary keys. Objects of these types support efficient pickling via the pickle module. Determining if an Object is Aware or Naive Objects of the date type are always naive. An object of type time or datetime may be aware or naive. A datetime object d is aware if both of the following hold:
d.tzinfo is not None
d.tzinfo.utcoffset(d) does not return None
Otherwise, d is naive. A time object t is aware if both of the following hold:
t.tzinfo is not None
t.tzinfo.utcoffset(None) does not return None. Otherwise, t is naive. The distinction between aware and naive doesn’t apply to timedelta objects. timedelta Objects A timedelta object represents a duration, the difference between two dates or times.
class datetime.timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)
All arguments are optional and default to 0. Arguments may be integers or floats, and may be positive or negative. Only days, seconds and microseconds are stored internally. Arguments are converted to those units: A millisecond is converted to 1000 microseconds. A minute is converted to 60 seconds. An hour is converted to 3600 seconds. A week is converted to 7 days. and days, seconds and microseconds are then normalized so that the representation is unique, with 0 <= microseconds < 1000000
0 <= seconds < 3600*24 (the number of seconds in one day) -999999999 <= days <= 999999999 The following example illustrates how any arguments besides days, seconds and microseconds are “merged” and normalized into those three resulting attributes: >>> from datetime import timedelta
>>> delta = timedelta(
... days=50,
... seconds=27,
... microseconds=10,
... milliseconds=29000,
... minutes=5,
... hours=8,
... weeks=2
... )
>>> # Only days, seconds, and microseconds remain
>>> delta
datetime.timedelta(days=64, seconds=29156, microseconds=10)
If any argument is a float and there are fractional microseconds, the fractional microseconds left over from all arguments are combined and their sum is rounded to the nearest microsecond using round-half-to-even tiebreaker. If no argument is a float, the conversion and normalization processes are exact (no information is lost). If the normalized value of days lies outside the indicated range, OverflowError is raised. Note that normalization of negative values may be surprising at first. For example: >>> from datetime import timedelta
>>> d = timedelta(microseconds=-1)
>>> (d.days, d.seconds, d.microseconds)
(-1, 86399, 999999)
Class attributes:
timedelta.min
The most negative timedelta object, timedelta(-999999999).
timedelta.max
The most positive timedelta object, timedelta(days=999999999,
hours=23, minutes=59, seconds=59, microseconds=999999).
timedelta.resolution
The smallest possible difference between non-equal timedelta objects, timedelta(microseconds=1).
Note that, because of normalization, timedelta.max > -timedelta.min. -timedelta.max is not representable as a timedelta object. Instance attributes (read-only):
Attribute Value
days Between -999999999 and 999999999 inclusive
seconds Between 0 and 86399 inclusive
microseconds Between 0 and 999999 inclusive Supported operations:
Operation Result
t1 = t2 + t3 Sum of t2 and t3. Afterwards t1-t2 == t3 and t1-t3 == t2 are true. (1)
t1 = t2 - t3 Difference of t2 and t3. Afterwards t1 == t2 - t3 and t2 == t1 + t3 are true. (1)(6)
t1 = t2 * i or t1 = i * t2 Delta multiplied by an integer. Afterwards t1 // i == t2 is true, provided i != 0.
In general, t1 * i == t1 * (i-1) + t1 is true. (1)
t1 = t2 * f or t1 = f * t2 Delta multiplied by a float. The result is rounded to the nearest multiple of timedelta.resolution using round-half-to-even.
f = t2 / t3 Division (3) of overall duration t2 by interval unit t3. Returns a float object.
t1 = t2 / f or t1 = t2 / i Delta divided by a float or an int. The result is rounded to the nearest multiple of timedelta.resolution using round-half-to-even.
t1 = t2 // i or t1 = t2 // t3 The floor is computed and the remainder (if any) is thrown away. In the second case, an integer is returned. (3)
t1 = t2 % t3 The remainder is computed as a timedelta object. (3)
q, r = divmod(t1, t2) Computes the quotient and the remainder: q = t1 // t2 (3) and r = t1 % t2. q is an integer and r is a timedelta object.
+t1 Returns a timedelta object with the same value. (2)
-t1 equivalent to timedelta(-t1.days, -t1.seconds, -t1.microseconds), and to t1* -1. (1)(4)
abs(t) equivalent to +t when t.days >= 0, and to -t when t.days < 0. (2)
str(t) Returns a string in the form [D day[s], ][H]H:MM:SS[.UUUUUU], where D is negative for negative t. (5)
repr(t) Returns a string representation of the timedelta object as a constructor call with canonical attribute values. Notes: This is exact but may overflow. This is exact and cannot overflow. Division by 0 raises ZeroDivisionError. -timedelta.max is not representable as a timedelta object.
String representations of timedelta objects are normalized similarly to their internal representation. This leads to somewhat unusual results for negative timedeltas. For example: >>> timedelta(hours=-5)
datetime.timedelta(days=-1, seconds=68400)
>>> print(_)
-1 day, 19:00:00
The expression t2 - t3 will always be equal to the expression t2 + (-t3) except when t3 is equal to timedelta.max; in that case the former will produce a result while the latter will overflow. In addition to the operations listed above, timedelta objects support certain additions and subtractions with date and datetime objects (see below). Changed in version 3.2: Floor division and true division of a timedelta object by another timedelta object are now supported, as are remainder operations and the divmod() function. True division and multiplication of a timedelta object by a float object are now supported. Comparisons of timedelta objects are supported, with some caveats. The comparisons == or != always return a bool, no matter the type of the compared object: >>> from datetime import timedelta
>>> delta1 = timedelta(seconds=57)
>>> delta2 = timedelta(hours=25, seconds=2)
>>> delta2 != delta1
True
>>> delta2 == 5
False
For all other comparisons (such as < and >), when a timedelta object is compared to an object of a different type, TypeError is raised: >>> delta2 > delta1
True
>>> delta2 > 5
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: '>' not supported between instances of 'datetime.timedelta' and 'int'
In Boolean contexts, a timedelta object is considered to be true if and only if it isn’t equal to timedelta(0). Instance methods:
timedelta.total_seconds()
Return the total number of seconds contained in the duration. Equivalent to td / timedelta(seconds=1). For interval units other than seconds, use the division form directly (e.g. td / timedelta(microseconds=1)). Note that for very large time intervals (greater than 270 years on most platforms) this method will lose microsecond accuracy. New in version 3.2.
Examples of usage: timedelta
An additional example of normalization: >>> # Components of another_year add up to exactly 365 days
>>> from datetime import timedelta
>>> year = timedelta(days=365)
>>> another_year = timedelta(weeks=40, days=84, hours=23,
... minutes=50, seconds=600)
>>> year == another_year
True
>>> year.total_seconds()
31536000.0
Examples of timedelta arithmetic: >>> from datetime import timedelta
>>> year = timedelta(days=365)
>>> ten_years = 10 * year
>>> ten_years
datetime.timedelta(days=3650)
>>> ten_years.days // 365
10
>>> nine_years = ten_years - year
>>> nine_years
datetime.timedelta(days=3285)
>>> three_years = nine_years // 3
>>> three_years, three_years.days // 365
(datetime.timedelta(days=1095), 3)
date Objects A date object represents a date (year, month and day) in an idealized calendar, the current Gregorian calendar indefinitely extended in both directions. January 1 of year 1 is called day number 1, January 2 of year 1 is called day number 2, and so on. 2
class datetime.date(year, month, day)
All arguments are required. Arguments must be integers, in the following ranges: MINYEAR <= year <= MAXYEAR 1 <= month <= 12 1 <= day <= number of days in the given month and year If an argument outside those ranges is given, ValueError is raised.
Other constructors, all class methods:
classmethod date.today()
Return the current local date. This is equivalent to date.fromtimestamp(time.time()).
classmethod date.fromtimestamp(timestamp)
Return the local date corresponding to the POSIX timestamp, such as is returned by time.time(). This may raise OverflowError, if the timestamp is out of the range of values supported by the platform C localtime() function, and OSError on localtime() failure. It’s common for this to be restricted to years from 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by fromtimestamp(). Changed in version 3.3: Raise OverflowError instead of ValueError if the timestamp is out of the range of values supported by the platform C localtime() function. Raise OSError instead of ValueError on localtime() failure.
classmethod date.fromordinal(ordinal)
Return the date corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1. ValueError is raised unless 1 <= ordinal <=
date.max.toordinal(). For any date d, date.fromordinal(d.toordinal()) == d.
classmethod date.fromisoformat(date_string)
Return a date corresponding to a date_string given in the format YYYY-MM-DD: >>> from datetime import date
>>> date.fromisoformat('2019-12-04')
datetime.date(2019, 12, 4)
This is the inverse of date.isoformat(). It only supports the format YYYY-MM-DD. New in version 3.7.
classmethod date.fromisocalendar(year, week, day)
Return a date corresponding to the ISO calendar date specified by year, week and day. This is the inverse of the function date.isocalendar(). New in version 3.8.
Class attributes:
date.min
The earliest representable date, date(MINYEAR, 1, 1).
date.max
The latest representable date, date(MAXYEAR, 12, 31).
date.resolution
The smallest possible difference between non-equal date objects, timedelta(days=1).
Instance attributes (read-only):
date.year
Between MINYEAR and MAXYEAR inclusive.
date.month
Between 1 and 12 inclusive.
date.day
Between 1 and the number of days in the given month of the given year.
Supported operations:
Operation Result
date2 = date1 + timedelta date2 is timedelta.days days removed from date1. (1)
date2 = date1 - timedelta Computes date2 such that date2 +
timedelta == date1. (2)
timedelta = date1 - date2 (3)
date1 < date2 date1 is considered less than date2 when date1 precedes date2 in time. (4) Notes:
date2 is moved forward in time if timedelta.days > 0, or backward if timedelta.days < 0. Afterward date2 - date1 == timedelta.days. timedelta.seconds and timedelta.microseconds are ignored. OverflowError is raised if date2.year would be smaller than MINYEAR or larger than MAXYEAR.
timedelta.seconds and timedelta.microseconds are ignored. This is exact, and cannot overflow. timedelta.seconds and timedelta.microseconds are 0, and date2 + timedelta == date1 after. In other words, date1 < date2 if and only if date1.toordinal() <
date2.toordinal(). Date comparison raises TypeError if the other comparand isn’t also a date object. However, NotImplemented is returned instead if the other comparand has a timetuple() attribute. This hook gives other kinds of date objects a chance at implementing mixed-type comparison. If not, when a date object is compared to an object of a different type, TypeError is raised unless the comparison is == or !=. The latter cases return False or True, respectively. In Boolean contexts, all date objects are considered to be true. Instance methods:
date.replace(year=self.year, month=self.month, day=self.day)
Return a date with the same value, except for those parameters given new values by whichever keyword arguments are specified. Example: >>> from datetime import date
>>> d = date(2002, 12, 31)
>>> d.replace(day=26)
datetime.date(2002, 12, 26)
date.timetuple()
Return a time.struct_time such as returned by time.localtime(). The hours, minutes and seconds are 0, and the DST flag is -1. d.timetuple() is equivalent to: time.struct_time((d.year, d.month, d.day, 0, 0, 0, d.weekday(), yday, -1))
where yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1 is the day number within the current year starting with 1 for January 1st.
date.toordinal()
Return the proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1. For any date object d, date.fromordinal(d.toordinal()) == d.
date.weekday()
Return the day of the week as an integer, where Monday is 0 and Sunday is 6. For example, date(2002, 12, 4).weekday() == 2, a Wednesday. See also isoweekday().
date.isoweekday()
Return the day of the week as an integer, where Monday is 1 and Sunday is 7. For example, date(2002, 12, 4).isoweekday() == 3, a Wednesday. See also weekday(), isocalendar().
date.isocalendar()
Return a named tuple object with three components: year, week and weekday. The ISO calendar is a widely used variant of the Gregorian calendar. 3 The ISO year consists of 52 or 53 full weeks, and where a week starts on a Monday and ends on a Sunday. The first week of an ISO year is the first (Gregorian) calendar week of a year containing a Thursday. This is called week number 1, and the ISO year of that Thursday is the same as its Gregorian year. For example, 2004 begins on a Thursday, so the first week of ISO year 2004 begins on Monday, 29 Dec 2003 and ends on Sunday, 4 Jan 2004: >>> from datetime import date
>>> date(2003, 12, 29).isocalendar()
datetime.IsoCalendarDate(year=2004, week=1, weekday=1)
>>> date(2004, 1, 4).isocalendar()
datetime.IsoCalendarDate(year=2004, week=1, weekday=7)
Changed in version 3.9: Result changed from a tuple to a named tuple.
date.isoformat()
Return a string representing the date in ISO 8601 format, YYYY-MM-DD: >>> from datetime import date
>>> date(2002, 12, 4).isoformat()
'2002-12-04'
This is the inverse of date.fromisoformat().
date.__str__()
For a date d, str(d) is equivalent to d.isoformat().
date.ctime()
Return a string representing the date: >>> from datetime import date
>>> date(2002, 12, 4).ctime()
'Wed Dec 4 00:00:00 2002'
d.ctime() is equivalent to: time.ctime(time.mktime(d.timetuple()))
on platforms where the native C ctime() function (which time.ctime() invokes, but which date.ctime() does not invoke) conforms to the C standard.
date.strftime(format)
Return a string representing the date, controlled by an explicit format string. Format codes referring to hours, minutes or seconds will see 0 values. For a complete list of formatting directives, see strftime() and strptime() Behavior.
date.__format__(format)
Same as date.strftime(). This makes it possible to specify a format string for a date object in formatted string literals and when using str.format(). For a complete list of formatting directives, see strftime() and strptime() Behavior.
Examples of Usage: date
Example of counting days to an event: >>> import time
>>> from datetime import date
>>> today = date.today()
>>> today
datetime.date(2007, 12, 5)
>>> today == date.fromtimestamp(time.time())
True
>>> my_birthday = date(today.year, 6, 24)
>>> if my_birthday < today:
... my_birthday = my_birthday.replace(year=today.year + 1)
>>> my_birthday
datetime.date(2008, 6, 24)
>>> time_to_birthday = abs(my_birthday - today)
>>> time_to_birthday.days
202
More examples of working with date: >>> from datetime import date
>>> d = date.fromordinal(730920) # 730920th day after 1. 1. 0001
>>> d
datetime.date(2002, 3, 11)
>>> # Methods related to formatting string output
>>> d.isoformat()
'2002-03-11'
>>> d.strftime("%d/%m/%y")
'11/03/02'
>>> d.strftime("%A %d. %B %Y")
'Monday 11. March 2002'
>>> d.ctime()
'Mon Mar 11 00:00:00 2002'
>>> 'The {1} is {0:%d}, the {2} is {0:%B}.'.format(d, "day", "month")
'The day is 11, the month is March.'
>>> # Methods for to extracting 'components' under different calendars
>>> t = d.timetuple()
>>> for i in t:
... print(i)
2002 # year
3 # month
11 # day
0
0
0
0 # weekday (0 = Monday)
70 # 70th day in the year
-1
>>> ic = d.isocalendar()
>>> for i in ic:
... print(i)
2002 # ISO year
11 # ISO week number
1 # ISO day number ( 1 = Monday )
>>> # A date object is immutable; all operations produce a new object
>>> d.replace(year=2005)
datetime.date(2005, 3, 11)
datetime Objects A datetime object is a single object containing all the information from a date object and a time object. Like a date object, datetime assumes the current Gregorian calendar extended in both directions; like a time object, datetime assumes there are exactly 3600*24 seconds in every day. Constructor:
class datetime.datetime(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)
The year, month and day arguments are required. tzinfo may be None, or an instance of a tzinfo subclass. The remaining arguments must be integers in the following ranges:
MINYEAR <= year <= MAXYEAR,
1 <= month <= 12,
1 <= day <= number of days in the given month and year,
0 <= hour < 24,
0 <= minute < 60,
0 <= second < 60,
0 <= microsecond < 1000000,
fold in [0, 1]. If an argument outside those ranges is given, ValueError is raised. New in version 3.6: Added the fold argument.
Other constructors, all class methods:
classmethod datetime.today()
Return the current local datetime, with tzinfo None. Equivalent to: datetime.fromtimestamp(time.time())
See also now(), fromtimestamp(). This method is functionally equivalent to now(), but without a tz parameter.
classmethod datetime.now(tz=None)
Return the current local date and time. If optional argument tz is None or not specified, this is like today(), but, if possible, supplies more precision than can be gotten from going through a time.time() timestamp (for example, this may be possible on platforms supplying the C gettimeofday() function). If tz is not None, it must be an instance of a tzinfo subclass, and the current date and time are converted to tz’s time zone. This function is preferred over today() and utcnow().
classmethod datetime.utcnow()
Return the current UTC date and time, with tzinfo None. This is like now(), but returns the current UTC date and time, as a naive datetime object. An aware current UTC datetime can be obtained by calling datetime.now(timezone.utc). See also now(). Warning Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC. As such, the recommended way to create an object representing the current time in UTC is by calling datetime.now(timezone.utc).
classmethod datetime.fromtimestamp(timestamp, tz=None)
Return the local date and time corresponding to the POSIX timestamp, such as is returned by time.time(). If optional argument tz is None or not specified, the timestamp is converted to the platform’s local date and time, and the returned datetime object is naive. If tz is not None, it must be an instance of a tzinfo subclass, and the timestamp is converted to tz’s time zone. fromtimestamp() may raise OverflowError, if the timestamp is out of the range of values supported by the platform C localtime() or gmtime() functions, and OSError on localtime() or gmtime() failure. It’s common for this to be restricted to years in 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by fromtimestamp(), and then it’s possible to have two timestamps differing by a second that yield identical datetime objects. This method is preferred over utcfromtimestamp(). Changed in version 3.3: Raise OverflowError instead of ValueError if the timestamp is out of the range of values supported by the platform C localtime() or gmtime() functions. Raise OSError instead of ValueError on localtime() or gmtime() failure. Changed in version 3.6: fromtimestamp() may return instances with fold set to 1.
classmethod datetime.utcfromtimestamp(timestamp)
Return the UTC datetime corresponding to the POSIX timestamp, with tzinfo None. (The resulting object is naive.) This may raise OverflowError, if the timestamp is out of the range of values supported by the platform C gmtime() function, and OSError on gmtime() failure. It’s common for this to be restricted to years in 1970 through 2038. To get an aware datetime object, call fromtimestamp(): datetime.fromtimestamp(timestamp, timezone.utc)
On the POSIX compliant platforms, it is equivalent to the following expression: datetime(1970, 1, 1, tzinfo=timezone.utc) + timedelta(seconds=timestamp)
except the latter formula always supports the full years range: between MINYEAR and MAXYEAR inclusive. Warning Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC. As such, the recommended way to create an object representing a specific timestamp in UTC is by calling datetime.fromtimestamp(timestamp, tz=timezone.utc). Changed in version 3.3: Raise OverflowError instead of ValueError if the timestamp is out of the range of values supported by the platform C gmtime() function. Raise OSError instead of ValueError on gmtime() failure.
classmethod datetime.fromordinal(ordinal)
Return the datetime corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1. ValueError is raised unless 1
<= ordinal <= datetime.max.toordinal(). The hour, minute, second and microsecond of the result are all 0, and tzinfo is None.
classmethod datetime.combine(date, time, tzinfo=self.tzinfo)
Return a new datetime object whose date components are equal to the given date object’s, and whose time components are equal to the given time object’s. If the tzinfo argument is provided, its value is used to set the tzinfo attribute of the result, otherwise the tzinfo attribute of the time argument is used. For any datetime object d, d == datetime.combine(d.date(), d.time(), d.tzinfo). If date is a datetime object, its time components and tzinfo attributes are ignored. Changed in version 3.6: Added the tzinfo argument.
classmethod datetime.fromisoformat(date_string)
Return a datetime corresponding to a date_string in one of the formats emitted by date.isoformat() and datetime.isoformat(). Specifically, this function supports strings in the format: YYYY-MM-DD[*HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]]
where * can match any single character. Caution This does not support parsing arbitrary ISO 8601 strings - it is only intended as the inverse operation of datetime.isoformat(). A more full-featured ISO 8601 parser, dateutil.parser.isoparse is available in the third-party package dateutil. Examples: >>> from datetime import datetime
>>> datetime.fromisoformat('2011-11-04')
datetime.datetime(2011, 11, 4, 0, 0)
>>> datetime.fromisoformat('2011-11-04T00:05:23')
datetime.datetime(2011, 11, 4, 0, 5, 23)
>>> datetime.fromisoformat('2011-11-04 00:05:23.283')
datetime.datetime(2011, 11, 4, 0, 5, 23, 283000)
>>> datetime.fromisoformat('2011-11-04 00:05:23.283+00:00')
datetime.datetime(2011, 11, 4, 0, 5, 23, 283000, tzinfo=datetime.timezone.utc)
>>> datetime.fromisoformat('2011-11-04T00:05:23+04:00')
datetime.datetime(2011, 11, 4, 0, 5, 23,
tzinfo=datetime.timezone(datetime.timedelta(seconds=14400)))
New in version 3.7.
classmethod datetime.fromisocalendar(year, week, day)
Return a datetime corresponding to the ISO calendar date specified by year, week and day. The non-date components of the datetime are populated with their normal default values. This is the inverse of the function datetime.isocalendar(). New in version 3.8.
classmethod datetime.strptime(date_string, format)
Return a datetime corresponding to date_string, parsed according to format. This is equivalent to: datetime(*(time.strptime(date_string, format)[0:6]))
ValueError is raised if the date_string and format can’t be parsed by time.strptime() or if it returns a value which isn’t a time tuple. For a complete list of formatting directives, see strftime() and strptime() Behavior.
Class attributes:
datetime.min
The earliest representable datetime, datetime(MINYEAR, 1, 1,
tzinfo=None).
datetime.max
The latest representable datetime, datetime(MAXYEAR, 12, 31, 23, 59,
59, 999999, tzinfo=None).
datetime.resolution
The smallest possible difference between non-equal datetime objects, timedelta(microseconds=1).
Instance attributes (read-only):
datetime.year
Between MINYEAR and MAXYEAR inclusive.
datetime.month
Between 1 and 12 inclusive.
datetime.day
Between 1 and the number of days in the given month of the given year.
datetime.hour
In range(24).
datetime.minute
In range(60).
datetime.second
In range(60).
datetime.microsecond
In range(1000000).
datetime.tzinfo
The object passed as the tzinfo argument to the datetime constructor, or None if none was passed.
datetime.fold
In [0, 1]. Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The value 0 (1) represents the earlier (later) of the two moments with the same wall time representation. New in version 3.6.
Supported operations:
Operation Result
datetime2 = datetime1 + timedelta (1)
datetime2 = datetime1 - timedelta (2)
timedelta = datetime1 - datetime2 (3)
datetime1 < datetime2 Compares datetime to datetime. (4) datetime2 is a duration of timedelta removed from datetime1, moving forward in time if timedelta.days > 0, or backward if timedelta.days < 0. The result has the same tzinfo attribute as the input datetime, and datetime2 - datetime1 == timedelta after. OverflowError is raised if datetime2.year would be smaller than MINYEAR or larger than MAXYEAR. Note that no time zone adjustments are done even if the input is an aware object. Computes the datetime2 such that datetime2 + timedelta == datetime1. As for addition, the result has the same tzinfo attribute as the input datetime, and no time zone adjustments are done even if the input is aware.
Subtraction of a datetime from a datetime is defined only if both operands are naive, or if both are aware. If one is aware and the other is naive, TypeError is raised. If both are naive, or both are aware and have the same tzinfo attribute, the tzinfo attributes are ignored, and the result is a timedelta object t such that datetime2 + t == datetime1. No time zone adjustments are done in this case. If both are aware and have different tzinfo attributes, a-b acts as if a and b were first converted to naive UTC datetimes first. The result is (a.replace(tzinfo=None) - a.utcoffset()) - (b.replace(tzinfo=None)
- b.utcoffset()) except that the implementation never overflows.
datetime1 is considered less than datetime2 when datetime1 precedes datetime2 in time. If one comparand is naive and the other is aware, TypeError is raised if an order comparison is attempted. For equality comparisons, naive instances are never equal to aware instances. If both comparands are aware, and have the same tzinfo attribute, the common tzinfo attribute is ignored and the base datetimes are compared. If both comparands are aware and have different tzinfo attributes, the comparands are first adjusted by subtracting their UTC offsets (obtained from self.utcoffset()). Changed in version 3.3: Equality comparisons between aware and naive datetime instances don’t raise TypeError. Note In order to stop comparison from falling back to the default scheme of comparing object addresses, datetime comparison normally raises TypeError if the other comparand isn’t also a datetime object. However, NotImplemented is returned instead if the other comparand has a timetuple() attribute. This hook gives other kinds of date objects a chance at implementing mixed-type comparison. If not, when a datetime object is compared to an object of a different type, TypeError is raised unless the comparison is == or !=. The latter cases return False or True, respectively. Instance methods:
datetime.date()
Return date object with same year, month and day.
datetime.time()
Return time object with same hour, minute, second, microsecond and fold. tzinfo is None. See also method timetz(). Changed in version 3.6: The fold value is copied to the returned time object.
datetime.timetz()
Return time object with same hour, minute, second, microsecond, fold, and tzinfo attributes. See also method time(). Changed in version 3.6: The fold value is copied to the returned time object.
datetime.replace(year=self.year, month=self.month, day=self.day, hour=self.hour, minute=self.minute, second=self.second, microsecond=self.microsecond, tzinfo=self.tzinfo, *, fold=0)
Return a datetime with the same attributes, except for those attributes given new values by whichever keyword arguments are specified. Note that tzinfo=None can be specified to create a naive datetime from an aware datetime with no conversion of date and time data. New in version 3.6: Added the fold argument.
datetime.astimezone(tz=None)
Return a datetime object with new tzinfo attribute tz, adjusting the date and time data so the result is the same UTC time as self, but in tz’s local time. If provided, tz must be an instance of a tzinfo subclass, and its utcoffset() and dst() methods must not return None. If self is naive, it is presumed to represent time in the system timezone. If called without arguments (or with tz=None) the system local timezone is assumed for the target timezone. The .tzinfo attribute of the converted datetime instance will be set to an instance of timezone with the zone name and offset obtained from the OS. If self.tzinfo is tz, self.astimezone(tz) is equal to self: no adjustment of date or time data is performed. Else the result is local time in the timezone tz, representing the same UTC time as self: after astz = dt.astimezone(tz), astz - astz.utcoffset() will have the same date and time data as dt - dt.utcoffset(). If you merely want to attach a time zone object tz to a datetime dt without adjustment of date and time data, use dt.replace(tzinfo=tz). If you merely want to remove the time zone object from an aware datetime dt without conversion of date and time data, use dt.replace(tzinfo=None). Note that the default tzinfo.fromutc() method can be overridden in a tzinfo subclass to affect the result returned by astimezone(). Ignoring error cases, astimezone() acts like: def astimezone(self, tz):
if self.tzinfo is tz:
return self
# Convert self to UTC, and attach the new time zone object.
utc = (self - self.utcoffset()).replace(tzinfo=tz)
# Convert from UTC to tz's local time.
return tz.fromutc(utc)
Changed in version 3.3: tz now can be omitted. Changed in version 3.6: The astimezone() method can now be called on naive instances that are presumed to represent system local time.
datetime.utcoffset()
If tzinfo is None, returns None, else returns self.tzinfo.utcoffset(self), and raises an exception if the latter doesn’t return None or a timedelta object with magnitude less than one day. Changed in version 3.7: The UTC offset is not restricted to a whole number of minutes.
datetime.dst()
If tzinfo is None, returns None, else returns self.tzinfo.dst(self), and raises an exception if the latter doesn’t return None or a timedelta object with magnitude less than one day. Changed in version 3.7: The DST offset is not restricted to a whole number of minutes.
datetime.tzname()
If tzinfo is None, returns None, else returns self.tzinfo.tzname(self), raises an exception if the latter doesn’t return None or a string object,
datetime.timetuple()
Return a time.struct_time such as returned by time.localtime(). d.timetuple() is equivalent to: time.struct_time((d.year, d.month, d.day,
d.hour, d.minute, d.second,
d.weekday(), yday, dst))
where yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1 is the day number within the current year starting with 1 for January 1st. The tm_isdst flag of the result is set according to the dst() method: tzinfo is None or dst() returns None, tm_isdst is set to -1; else if dst() returns a non-zero value, tm_isdst is set to 1; else tm_isdst is set to 0.
datetime.utctimetuple()
If datetime instance d is naive, this is the same as d.timetuple() except that tm_isdst is forced to 0 regardless of what d.dst() returns. DST is never in effect for a UTC time. If d is aware, d is normalized to UTC time, by subtracting d.utcoffset(), and a time.struct_time for the normalized time is returned. tm_isdst is forced to 0. Note that an OverflowError may be raised if d.year was MINYEAR or MAXYEAR and UTC adjustment spills over a year boundary. Warning Because naive datetime objects are treated by many datetime methods as local times, it is preferred to use aware datetimes to represent times in UTC; as a result, using utcfromtimetuple may give misleading results. If you have a naive datetime representing UTC, use datetime.replace(tzinfo=timezone.utc) to make it aware, at which point you can use datetime.timetuple().
datetime.toordinal()
Return the proleptic Gregorian ordinal of the date. The same as self.date().toordinal().
datetime.timestamp()
Return POSIX timestamp corresponding to the datetime instance. The return value is a float similar to that returned by time.time(). Naive datetime instances are assumed to represent local time and this method relies on the platform C mktime() function to perform the conversion. Since datetime supports wider range of values than mktime() on many platforms, this method may raise OverflowError for times far in the past or far in the future. For aware datetime instances, the return value is computed as: (dt - datetime(1970, 1, 1, tzinfo=timezone.utc)).total_seconds()
New in version 3.3. Changed in version 3.6: The timestamp() method uses the fold attribute to disambiguate the times during a repeated interval. Note There is no method to obtain the POSIX timestamp directly from a naive datetime instance representing UTC time. If your application uses this convention and your system timezone is not set to UTC, you can obtain the POSIX timestamp by supplying tzinfo=timezone.utc: timestamp = dt.replace(tzinfo=timezone.utc).timestamp()
or by calculating the timestamp directly: timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1)
datetime.weekday()
Return the day of the week as an integer, where Monday is 0 and Sunday is 6. The same as self.date().weekday(). See also isoweekday().
datetime.isoweekday()
Return the day of the week as an integer, where Monday is 1 and Sunday is 7. The same as self.date().isoweekday(). See also weekday(), isocalendar().
datetime.isocalendar()
Return a named tuple with three components: year, week and weekday. The same as self.date().isocalendar().
datetime.isoformat(sep='T', timespec='auto')
Return a string representing the date and time in ISO 8601 format:
YYYY-MM-DDTHH:MM:SS.ffffff, if microsecond is not 0
YYYY-MM-DDTHH:MM:SS, if microsecond is 0 If utcoffset() does not return None, a string is appended, giving the UTC offset:
YYYY-MM-DDTHH:MM:SS.ffffff+HH:MM[:SS[.ffffff]], if microsecond is not 0
YYYY-MM-DDTHH:MM:SS+HH:MM[:SS[.ffffff]], if microsecond is 0 Examples: >>> from datetime import datetime, timezone
>>> datetime(2019, 5, 18, 15, 17, 8, 132263).isoformat()
'2019-05-18T15:17:08.132263'
>>> datetime(2019, 5, 18, 15, 17, tzinfo=timezone.utc).isoformat()
'2019-05-18T15:17:00+00:00'
The optional argument sep (default 'T') is a one-character separator, placed between the date and time portions of the result. For example: >>> from datetime import tzinfo, timedelta, datetime
>>> class TZ(tzinfo):
... """A time zone with an arbitrary, constant -06:39 offset."""
... def utcoffset(self, dt):
... return timedelta(hours=-6, minutes=-39)
...
>>> datetime(2002, 12, 25, tzinfo=TZ()).isoformat(' ')
'2002-12-25 00:00:00-06:39'
>>> datetime(2009, 11, 27, microsecond=100, tzinfo=TZ()).isoformat()
'2009-11-27T00:00:00.000100-06:39'
The optional argument timespec specifies the number of additional components of the time to include (the default is 'auto'). It can be one of the following:
'auto': Same as 'seconds' if microsecond is 0, same as 'microseconds' otherwise.
'hours': Include the hour in the two-digit HH format.
'minutes': Include hour and minute in HH:MM format.
'seconds': Include hour, minute, and second in HH:MM:SS format.
'milliseconds': Include full time, but truncate fractional second part to milliseconds. HH:MM:SS.sss format.
'microseconds': Include full time in HH:MM:SS.ffffff format. Note Excluded time components are truncated, not rounded. ValueError will be raised on an invalid timespec argument: >>> from datetime import datetime
>>> datetime.now().isoformat(timespec='minutes')
'2002-12-25T00:00'
>>> dt = datetime(2015, 1, 1, 12, 30, 59, 0)
>>> dt.isoformat(timespec='microseconds')
'2015-01-01T12:30:59.000000'
New in version 3.6: Added the timespec argument.
datetime.__str__()
For a datetime instance d, str(d) is equivalent to d.isoformat(' ').
datetime.ctime()
Return a string representing the date and time: >>> from datetime import datetime
>>> datetime(2002, 12, 4, 20, 30, 40).ctime()
'Wed Dec 4 20:30:40 2002'
The output string will not include time zone information, regardless of whether the input is aware or naive. d.ctime() is equivalent to: time.ctime(time.mktime(d.timetuple()))
on platforms where the native C ctime() function (which time.ctime() invokes, but which datetime.ctime() does not invoke) conforms to the C standard.
datetime.strftime(format)
Return a string representing the date and time, controlled by an explicit format string. For a complete list of formatting directives, see strftime() and strptime() Behavior.
datetime.__format__(format)
Same as datetime.strftime(). This makes it possible to specify a format string for a datetime object in formatted string literals and when using str.format(). For a complete list of formatting directives, see strftime() and strptime() Behavior.
Examples of Usage: datetime
Examples of working with datetime objects: >>> from datetime import datetime, date, time, timezone
>>> # Using datetime.combine()
>>> d = date(2005, 7, 14)
>>> t = time(12, 30)
>>> datetime.combine(d, t)
datetime.datetime(2005, 7, 14, 12, 30)
>>> # Using datetime.now()
>>> datetime.now()
datetime.datetime(2007, 12, 6, 16, 29, 43, 79043) # GMT +1
>>> datetime.now(timezone.utc)
datetime.datetime(2007, 12, 6, 15, 29, 43, 79060, tzinfo=datetime.timezone.utc)
>>> # Using datetime.strptime()
>>> dt = datetime.strptime("21/11/06 16:30", "%d/%m/%y %H:%M")
>>> dt
datetime.datetime(2006, 11, 21, 16, 30)
>>> # Using datetime.timetuple() to get tuple of all attributes
>>> tt = dt.timetuple()
>>> for it in tt:
... print(it)
...
2006 # year
11 # month
21 # day
16 # hour
30 # minute
0 # second
1 # weekday (0 = Monday)
325 # number of days since 1st January
-1 # dst - method tzinfo.dst() returned None
>>> # Date in ISO format
>>> ic = dt.isocalendar()
>>> for it in ic:
... print(it)
...
2006 # ISO year
47 # ISO week
2 # ISO weekday
>>> # Formatting a datetime
>>> dt.strftime("%A, %d. %B %Y %I:%M%p")
'Tuesday, 21. November 2006 04:30PM'
>>> 'The {1} is {0:%d}, the {2} is {0:%B}, the {3} is {0:%I:%M%p}.'.format(dt, "day", "month", "time")
'The day is 21, the month is November, the time is 04:30PM.'
The example below defines a tzinfo subclass capturing time zone information for Kabul, Afghanistan, which used +4 UTC until 1945 and then +4:30 UTC thereafter: from datetime import timedelta, datetime, tzinfo, timezone
class KabulTz(tzinfo):
# Kabul used +4 until 1945, when they moved to +4:30
UTC_MOVE_DATE = datetime(1944, 12, 31, 20, tzinfo=timezone.utc)
def utcoffset(self, dt):
if dt.year < 1945:
return timedelta(hours=4)
elif (1945, 1, 1, 0, 0) <= dt.timetuple()[:5] < (1945, 1, 1, 0, 30):
# An ambiguous ("imaginary") half-hour range representing
# a 'fold' in time due to the shift from +4 to +4:30.
# If dt falls in the imaginary range, use fold to decide how
# to resolve. See PEP495.
return timedelta(hours=4, minutes=(30 if dt.fold else 0))
else:
return timedelta(hours=4, minutes=30)
def fromutc(self, dt):
# Follow same validations as in datetime.tzinfo
if not isinstance(dt, datetime):
raise TypeError("fromutc() requires a datetime argument")
if dt.tzinfo is not self:
raise ValueError("dt.tzinfo is not self")
# A custom implementation is required for fromutc as
# the input to this function is a datetime with utc values
# but with a tzinfo set to self.
# See datetime.astimezone or fromtimestamp.
if dt.replace(tzinfo=timezone.utc) >= self.UTC_MOVE_DATE:
return dt + timedelta(hours=4, minutes=30)
else:
return dt + timedelta(hours=4)
def dst(self, dt):
# Kabul does not observe daylight saving time.
return timedelta(0)
def tzname(self, dt):
if dt >= self.UTC_MOVE_DATE:
return "+04:30"
return "+04"
Usage of KabulTz from above: >>> tz1 = KabulTz()
>>> # Datetime before the change
>>> dt1 = datetime(1900, 11, 21, 16, 30, tzinfo=tz1)
>>> print(dt1.utcoffset())
4:00:00
>>> # Datetime after the change
>>> dt2 = datetime(2006, 6, 14, 13, 0, tzinfo=tz1)
>>> print(dt2.utcoffset())
4:30:00
>>> # Convert datetime to another time zone
>>> dt3 = dt2.astimezone(timezone.utc)
>>> dt3
datetime.datetime(2006, 6, 14, 8, 30, tzinfo=datetime.timezone.utc)
>>> dt2
datetime.datetime(2006, 6, 14, 13, 0, tzinfo=KabulTz())
>>> dt2 == dt3
True
time Objects A time object represents a (local) time of day, independent of any particular day, and subject to adjustment via a tzinfo object.
class datetime.time(hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)
All arguments are optional. tzinfo may be None, or an instance of a tzinfo subclass. The remaining arguments must be integers in the following ranges:
0 <= hour < 24,
0 <= minute < 60,
0 <= second < 60,
0 <= microsecond < 1000000,
fold in [0, 1]. If an argument outside those ranges is given, ValueError is raised. All default to 0 except tzinfo, which defaults to None.
Class attributes:
time.min
The earliest representable time, time(0, 0, 0, 0).
time.max
The latest representable time, time(23, 59, 59, 999999).
time.resolution
The smallest possible difference between non-equal time objects, timedelta(microseconds=1), although note that arithmetic on time objects is not supported.
Instance attributes (read-only):
time.hour
In range(24).
time.minute
In range(60).
time.second
In range(60).
time.microsecond
In range(1000000).
time.tzinfo
The object passed as the tzinfo argument to the time constructor, or None if none was passed.
time.fold
In [0, 1]. Used to disambiguate wall times during a repeated interval. (A repeated interval occurs when clocks are rolled back at the end of daylight saving time or when the UTC offset for the current zone is decreased for political reasons.) The value 0 (1) represents the earlier (later) of the two moments with the same wall time representation. New in version 3.6.
time objects support comparison of time to time, where a is considered less than b when a precedes b in time. If one comparand is naive and the other is aware, TypeError is raised if an order comparison is attempted. For equality comparisons, naive instances are never equal to aware instances. If both comparands are aware, and have the same tzinfo attribute, the common tzinfo attribute is ignored and the base times are compared. If both comparands are aware and have different tzinfo attributes, the comparands are first adjusted by subtracting their UTC offsets (obtained from self.utcoffset()). In order to stop mixed-type comparisons from falling back to the default comparison by object address, when a time object is compared to an object of a different type, TypeError is raised unless the comparison is == or !=. The latter cases return False or True, respectively. Changed in version 3.3: Equality comparisons between aware and naive time instances don’t raise TypeError. In Boolean contexts, a time object is always considered to be true. Changed in version 3.5: Before Python 3.5, a time object was considered to be false if it represented midnight in UTC. This behavior was considered obscure and error-prone and has been removed in Python 3.5. See bpo-13936 for full details. Other constructor:
classmethod time.fromisoformat(time_string)
Return a time corresponding to a time_string in one of the formats emitted by time.isoformat(). Specifically, this function supports strings in the format: HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]
Caution This does not support parsing arbitrary ISO 8601 strings. It is only intended as the inverse operation of time.isoformat(). Examples: >>> from datetime import time
>>> time.fromisoformat('04:23:01')
datetime.time(4, 23, 1)
>>> time.fromisoformat('04:23:01.000384')
datetime.time(4, 23, 1, 384)
>>> time.fromisoformat('04:23:01+04:00')
datetime.time(4, 23, 1, tzinfo=datetime.timezone(datetime.timedelta(seconds=14400)))
New in version 3.7.
Instance methods:
time.replace(hour=self.hour, minute=self.minute, second=self.second, microsecond=self.microsecond, tzinfo=self.tzinfo, *, fold=0)
Return a time with the same value, except for those attributes given new values by whichever keyword arguments are specified. Note that tzinfo=None can be specified to create a naive time from an aware time, without conversion of the time data. New in version 3.6: Added the fold argument.
time.isoformat(timespec='auto')
Return a string representing the time in ISO 8601 format, one of:
HH:MM:SS.ffffff, if microsecond is not 0
HH:MM:SS, if microsecond is 0
HH:MM:SS.ffffff+HH:MM[:SS[.ffffff]], if utcoffset() does not return None
HH:MM:SS+HH:MM[:SS[.ffffff]], if microsecond is 0 and utcoffset() does not return None
The optional argument timespec specifies the number of additional components of the time to include (the default is 'auto'). It can be one of the following:
'auto': Same as 'seconds' if microsecond is 0, same as 'microseconds' otherwise.
'hours': Include the hour in the two-digit HH format.
'minutes': Include hour and minute in HH:MM format.
'seconds': Include hour, minute, and second in HH:MM:SS format.
'milliseconds': Include full time, but truncate fractional second part to milliseconds. HH:MM:SS.sss format.
'microseconds': Include full time in HH:MM:SS.ffffff format. Note Excluded time components are truncated, not rounded. ValueError will be raised on an invalid timespec argument. Example: >>> from datetime import time
>>> time(hour=12, minute=34, second=56, microsecond=123456).isoformat(timespec='minutes')
'12:34'
>>> dt = time(hour=12, minute=34, second=56, microsecond=0)
>>> dt.isoformat(timespec='microseconds')
'12:34:56.000000'
>>> dt.isoformat(timespec='auto')
'12:34:56'
New in version 3.6: Added the timespec argument.
time.__str__()
For a time t, str(t) is equivalent to t.isoformat().
time.strftime(format)
Return a string representing the time, controlled by an explicit format string. For a complete list of formatting directives, see strftime() and strptime() Behavior.
time.__format__(format)
Same as time.strftime(). This makes it possible to specify a format string for a time object in formatted string literals and when using str.format(). For a complete list of formatting directives, see strftime() and strptime() Behavior.
time.utcoffset()
If tzinfo is None, returns None, else returns self.tzinfo.utcoffset(None), and raises an exception if the latter doesn’t return None or a timedelta object with magnitude less than one day. Changed in version 3.7: The UTC offset is not restricted to a whole number of minutes.
time.dst()
If tzinfo is None, returns None, else returns self.tzinfo.dst(None), and raises an exception if the latter doesn’t return None, or a timedelta object with magnitude less than one day. Changed in version 3.7: The DST offset is not restricted to a whole number of minutes.
time.tzname()
If tzinfo is None, returns None, else returns self.tzinfo.tzname(None), or raises an exception if the latter doesn’t return None or a string object.
Examples of Usage: time
Examples of working with a time object: >>> from datetime import time, tzinfo, timedelta
>>> class TZ1(tzinfo):
... def utcoffset(self, dt):
... return timedelta(hours=1)
... def dst(self, dt):
... return timedelta(0)
... def tzname(self,dt):
... return "+01:00"
... def __repr__(self):
... return f"{self.__class__.__name__}()"
...
>>> t = time(12, 10, 30, tzinfo=TZ1())
>>> t
datetime.time(12, 10, 30, tzinfo=TZ1())
>>> t.isoformat()
'12:10:30+01:00'
>>> t.dst()
datetime.timedelta(0)
>>> t.tzname()
'+01:00'
>>> t.strftime("%H:%M:%S %Z")
'12:10:30 +01:00'
>>> 'The {} is {:%H:%M}.'.format("time", t)
'The time is 12:10.'
tzinfo Objects
class datetime.tzinfo
This is an abstract base class, meaning that this class should not be instantiated directly. Define a subclass of tzinfo to capture information about a particular time zone. An instance of (a concrete subclass of) tzinfo can be passed to the constructors for datetime and time objects. The latter objects view their attributes as being in local time, and the tzinfo object supports methods revealing offset of local time from UTC, the name of the time zone, and DST offset, all relative to a date or time object passed to them. You need to derive a concrete subclass, and (at least) supply implementations of the standard tzinfo methods needed by the datetime methods you use. The datetime module provides timezone, a simple concrete subclass of tzinfo which can represent timezones with fixed offset from UTC such as UTC itself or North American EST and EDT. Special requirement for pickling: A tzinfo subclass must have an __init__() method that can be called with no arguments, otherwise it can be pickled but possibly not unpickled again. This is a technical requirement that may be relaxed in the future. A concrete subclass of tzinfo may need to implement the following methods. Exactly which methods are needed depends on the uses made of aware datetime objects. If in doubt, simply implement all of them.
tzinfo.utcoffset(dt)
Return offset of local time from UTC, as a timedelta object that is positive east of UTC. If local time is west of UTC, this should be negative. This represents the total offset from UTC; for example, if a tzinfo object represents both time zone and DST adjustments, utcoffset() should return their sum. If the UTC offset isn’t known, return None. Else the value returned must be a timedelta object strictly between -timedelta(hours=24) and timedelta(hours=24) (the magnitude of the offset must be less than one day). Most implementations of utcoffset() will probably look like one of these two: return CONSTANT # fixed-offset class
return CONSTANT + self.dst(dt) # daylight-aware class
If utcoffset() does not return None, dst() should not return None either. The default implementation of utcoffset() raises NotImplementedError. Changed in version 3.7: The UTC offset is not restricted to a whole number of minutes.
tzinfo.dst(dt)
Return the daylight saving time (DST) adjustment, as a timedelta object or None if DST information isn’t known. Return timedelta(0) if DST is not in effect. If DST is in effect, return the offset as a timedelta object (see utcoffset() for details). Note that DST offset, if applicable, has already been added to the UTC offset returned by utcoffset(), so there’s no need to consult dst() unless you’re interested in obtaining DST info separately. For example, datetime.timetuple() calls its tzinfo attribute’s dst() method to determine how the tm_isdst flag should be set, and tzinfo.fromutc() calls dst() to account for DST changes when crossing time zones. An instance tz of a tzinfo subclass that models both standard and daylight times must be consistent in this sense: tz.utcoffset(dt) - tz.dst(dt) must return the same result for every datetime dt with dt.tzinfo ==
tz For sane tzinfo subclasses, this expression yields the time zone’s “standard offset”, which should not depend on the date or the time, but only on geographic location. The implementation of datetime.astimezone() relies on this, but cannot detect violations; it’s the programmer’s responsibility to ensure it. If a tzinfo subclass cannot guarantee this, it may be able to override the default implementation of tzinfo.fromutc() to work correctly with astimezone() regardless. Most implementations of dst() will probably look like one of these two: def dst(self, dt):
# a fixed-offset class: doesn't account for DST
return timedelta(0)
or: def dst(self, dt):
# Code to set dston and dstoff to the time zone's DST
# transition times based on the input dt.year, and expressed
# in standard local time.
if dston <= dt.replace(tzinfo=None) < dstoff:
return timedelta(hours=1)
else:
return timedelta(0)
The default implementation of dst() raises NotImplementedError. Changed in version 3.7: The DST offset is not restricted to a whole number of minutes.
tzinfo.tzname(dt)
Return the time zone name corresponding to the datetime object dt, as a string. Nothing about string names is defined by the datetime module, and there’s no requirement that it mean anything in particular. For example, “GMT”, “UTC”, “-500”, “-5:00”, “EDT”, “US/Eastern”, “America/New York” are all valid replies. Return None if a string name isn’t known. Note that this is a method rather than a fixed string primarily because some tzinfo subclasses will wish to return different names depending on the specific value of dt passed, especially if the tzinfo class is accounting for daylight time. The default implementation of tzname() raises NotImplementedError.
These methods are called by a datetime or time object, in response to their methods of the same names. A datetime object passes itself as the argument, and a time object passes None as the argument. A tzinfo subclass’s methods should therefore be prepared to accept a dt argument of None, or of class datetime. When None is passed, it’s up to the class designer to decide the best response. For example, returning None is appropriate if the class wishes to say that time objects don’t participate in the tzinfo protocols. It may be more useful for utcoffset(None) to return the standard UTC offset, as there is no other convention for discovering the standard offset. When a datetime object is passed in response to a datetime method, dt.tzinfo is the same object as self. tzinfo methods can rely on this, unless user code calls tzinfo methods directly. The intent is that the tzinfo methods interpret dt as being in local time, and not need worry about objects in other timezones. There is one more tzinfo method that a subclass may wish to override:
tzinfo.fromutc(dt)
This is called from the default datetime.astimezone() implementation. When called from that, dt.tzinfo is self, and dt’s date and time data are to be viewed as expressing a UTC time. The purpose of fromutc() is to adjust the date and time data, returning an equivalent datetime in self’s local time. Most tzinfo subclasses should be able to inherit the default fromutc() implementation without problems. It’s strong enough to handle fixed-offset time zones, and time zones accounting for both standard and daylight time, and the latter even if the DST transition times differ in different years. An example of a time zone the default fromutc() implementation may not handle correctly in all cases is one where the standard offset (from UTC) depends on the specific date and time passed, which can happen for political reasons. The default implementations of astimezone() and fromutc() may not produce the result you want if the result is one of the hours straddling the moment the standard offset changes. Skipping code for error cases, the default fromutc() implementation acts like: def fromutc(self, dt):
# raise ValueError error if dt.tzinfo is not self
dtoff = dt.utcoffset()
dtdst = dt.dst()
# raise ValueError if dtoff is None or dtdst is None
delta = dtoff - dtdst # this is self's standard offset
if delta:
dt += delta # convert to standard local time
dtdst = dt.dst()
# raise ValueError if dtdst is None
if dtdst:
return dt + dtdst
else:
return dt
In the following tzinfo_examples.py file there are some examples of tzinfo classes: from datetime import tzinfo, timedelta, datetime
ZERO = timedelta(0)
HOUR = timedelta(hours=1)
SECOND = timedelta(seconds=1)
# A class capturing the platform's idea of local time.
# (May result in wrong values on historical times in
# timezones where UTC offset and/or the DST rules had
# changed in the past.)
import time as _time
STDOFFSET = timedelta(seconds = -_time.timezone)
if _time.daylight:
DSTOFFSET = timedelta(seconds = -_time.altzone)
else:
DSTOFFSET = STDOFFSET
DSTDIFF = DSTOFFSET - STDOFFSET
class LocalTimezone(tzinfo):
def fromutc(self, dt):
assert dt.tzinfo is self
stamp = (dt - datetime(1970, 1, 1, tzinfo=self)) // SECOND
args = _time.localtime(stamp)[:6]
dst_diff = DSTDIFF // SECOND
# Detect fold
fold = (args == _time.localtime(stamp - dst_diff))
return datetime(*args, microsecond=dt.microsecond,
tzinfo=self, fold=fold)
def utcoffset(self, dt):
if self._isdst(dt):
return DSTOFFSET
else:
return STDOFFSET
def dst(self, dt):
if self._isdst(dt):
return DSTDIFF
else:
return ZERO
def tzname(self, dt):
return _time.tzname[self._isdst(dt)]
def _isdst(self, dt):
tt = (dt.year, dt.month, dt.day,
dt.hour, dt.minute, dt.second,
dt.weekday(), 0, 0)
stamp = _time.mktime(tt)
tt = _time.localtime(stamp)
return tt.tm_isdst > 0
Local = LocalTimezone()
# A complete implementation of current DST rules for major US time zones.
def first_sunday_on_or_after(dt):
days_to_go = 6 - dt.weekday()
if days_to_go:
dt += timedelta(days_to_go)
return dt
# US DST Rules
#
# This is a simplified (i.e., wrong for a few cases) set of rules for US
# DST start and end times. For a complete and up-to-date set of DST rules
# and timezone definitions, visit the Olson Database (or try pytz):
# http://www.twinsun.com/tz/tz-link.htm
# http://sourceforge.net/projects/pytz/ (might not be up-to-date)
#
# In the US, since 2007, DST starts at 2am (standard time) on the second
# Sunday in March, which is the first Sunday on or after Mar 8.
DSTSTART_2007 = datetime(1, 3, 8, 2)
# and ends at 2am (DST time) on the first Sunday of Nov.
DSTEND_2007 = datetime(1, 11, 1, 2)
# From 1987 to 2006, DST used to start at 2am (standard time) on the first
# Sunday in April and to end at 2am (DST time) on the last
# Sunday of October, which is the first Sunday on or after Oct 25.
DSTSTART_1987_2006 = datetime(1, 4, 1, 2)
DSTEND_1987_2006 = datetime(1, 10, 25, 2)
# From 1967 to 1986, DST used to start at 2am (standard time) on the last
# Sunday in April (the one on or after April 24) and to end at 2am (DST time)
# on the last Sunday of October, which is the first Sunday
# on or after Oct 25.
DSTSTART_1967_1986 = datetime(1, 4, 24, 2)
DSTEND_1967_1986 = DSTEND_1987_2006
def us_dst_range(year):
# Find start and end times for US DST. For years before 1967, return
# start = end for no DST.
if 2006 < year:
dststart, dstend = DSTSTART_2007, DSTEND_2007
elif 1986 < year < 2007:
dststart, dstend = DSTSTART_1987_2006, DSTEND_1987_2006
elif 1966 < year < 1987:
dststart, dstend = DSTSTART_1967_1986, DSTEND_1967_1986
else:
return (datetime(year, 1, 1), ) * 2
start = first_sunday_on_or_after(dststart.replace(year=year))
end = first_sunday_on_or_after(dstend.replace(year=year))
return start, end
class USTimeZone(tzinfo):
def __init__(self, hours, reprname, stdname, dstname):
self.stdoffset = timedelta(hours=hours)
self.reprname = reprname
self.stdname = stdname
self.dstname = dstname
def __repr__(self):
return self.reprname
def tzname(self, dt):
if self.dst(dt):
return self.dstname
else:
return self.stdname
def utcoffset(self, dt):
return self.stdoffset + self.dst(dt)
def dst(self, dt):
if dt is None or dt.tzinfo is None:
# An exception may be sensible here, in one or both cases.
# It depends on how you want to treat them. The default
# fromutc() implementation (called by the default astimezone()
# implementation) passes a datetime with dt.tzinfo is self.
return ZERO
assert dt.tzinfo is self
start, end = us_dst_range(dt.year)
# Can't compare naive to aware objects, so strip the timezone from
# dt first.
dt = dt.replace(tzinfo=None)
if start + HOUR <= dt < end - HOUR:
# DST is in effect.
return HOUR
if end - HOUR <= dt < end:
# Fold (an ambiguous hour): use dt.fold to disambiguate.
return ZERO if dt.fold else HOUR
if start <= dt < start + HOUR:
# Gap (a non-existent hour): reverse the fold rule.
return HOUR if dt.fold else ZERO
# DST is off.
return ZERO
def fromutc(self, dt):
assert dt.tzinfo is self
start, end = us_dst_range(dt.year)
start = start.replace(tzinfo=self)
end = end.replace(tzinfo=self)
std_time = dt + self.stdoffset
dst_time = std_time + HOUR
if end <= dst_time < end + HOUR:
# Repeated hour
return std_time.replace(fold=1)
if std_time < start or dst_time >= end:
# Standard time
return std_time
if start <= std_time < end - HOUR:
# Daylight saving time
return dst_time
Eastern = USTimeZone(-5, "Eastern", "EST", "EDT")
Central = USTimeZone(-6, "Central", "CST", "CDT")
Mountain = USTimeZone(-7, "Mountain", "MST", "MDT")
Pacific = USTimeZone(-8, "Pacific", "PST", "PDT")
Note that there are unavoidable subtleties twice per year in a tzinfo subclass accounting for both standard and daylight time, at the DST transition points. For concreteness, consider US Eastern (UTC -0500), where EDT begins the minute after 1:59 (EST) on the second Sunday in March, and ends the minute after 1:59 (EDT) on the first Sunday in November: UTC 3:MM 4:MM 5:MM 6:MM 7:MM 8:MM
EST 22:MM 23:MM 0:MM 1:MM 2:MM 3:MM
EDT 23:MM 0:MM 1:MM 2:MM 3:MM 4:MM
start 22:MM 23:MM 0:MM 1:MM 3:MM 4:MM
end 23:MM 0:MM 1:MM 1:MM 2:MM 3:MM
When DST starts (the “start” line), the local wall clock leaps from 1:59 to 3:00. A wall time of the form 2:MM doesn’t really make sense on that day, so astimezone(Eastern) won’t deliver a result with hour == 2 on the day DST begins. For example, at the Spring forward transition of 2016, we get: >>> from datetime import datetime, timezone
>>> from tzinfo_examples import HOUR, Eastern
>>> u0 = datetime(2016, 3, 13, 5, tzinfo=timezone.utc)
>>> for i in range(4):
... u = u0 + i*HOUR
... t = u.astimezone(Eastern)
... print(u.time(), 'UTC =', t.time(), t.tzname())
...
05:00:00 UTC = 00:00:00 EST
06:00:00 UTC = 01:00:00 EST
07:00:00 UTC = 03:00:00 EDT
08:00:00 UTC = 04:00:00 EDT
When DST ends (the “end” line), there’s a potentially worse problem: there’s an hour that can’t be spelled unambiguously in local wall time: the last hour of daylight time. In Eastern, that’s times of the form 5:MM UTC on the day daylight time ends. The local wall clock leaps from 1:59 (daylight time) back to 1:00 (standard time) again. Local times of the form 1:MM are ambiguous. astimezone() mimics the local clock’s behavior by mapping two adjacent UTC hours into the same local hour then. In the Eastern example, UTC times of the form 5:MM and 6:MM both map to 1:MM when converted to Eastern, but earlier times have the fold attribute set to 0 and the later times have it set to 1. For example, at the Fall back transition of 2016, we get: >>> u0 = datetime(2016, 11, 6, 4, tzinfo=timezone.utc)
>>> for i in range(4):
... u = u0 + i*HOUR
... t = u.astimezone(Eastern)
... print(u.time(), 'UTC =', t.time(), t.tzname(), t.fold)
...
04:00:00 UTC = 00:00:00 EDT 0
05:00:00 UTC = 01:00:00 EDT 0
06:00:00 UTC = 01:00:00 EST 1
07:00:00 UTC = 02:00:00 EST 0
Note that the datetime instances that differ only by the value of the fold attribute are considered equal in comparisons. Applications that can’t bear wall-time ambiguities should explicitly check the value of the fold attribute or avoid using hybrid tzinfo subclasses; there are no ambiguities when using timezone, or any other fixed-offset tzinfo subclass (such as a class representing only EST (fixed offset -5 hours), or only EDT (fixed offset -4 hours)). See also dateutil.tz
The datetime module has a basic timezone class (for handling arbitrary fixed offsets from UTC) and its timezone.utc attribute (a UTC timezone instance). dateutil.tz library brings the IANA timezone database (also known as the Olson database) to Python, and its usage is recommended. IANA timezone database
The Time Zone Database (often called tz, tzdata or zoneinfo) contains code and data that represent the history of local time for many representative locations around the globe. It is updated periodically to reflect changes made by political bodies to time zone boundaries, UTC offsets, and daylight-saving rules. timezone Objects The timezone class is a subclass of tzinfo, each instance of which represents a timezone defined by a fixed offset from UTC. Objects of this class cannot be used to represent timezone information in the locations where different offsets are used in different days of the year or where historical changes have been made to civil time.
class datetime.timezone(offset, name=None)
The offset argument must be specified as a timedelta object representing the difference between the local time and UTC. It must be strictly between -timedelta(hours=24) and timedelta(hours=24), otherwise ValueError is raised. The name argument is optional. If specified it must be a string that will be used as the value returned by the datetime.tzname() method. New in version 3.2. Changed in version 3.7: The UTC offset is not restricted to a whole number of minutes.
timezone.utcoffset(dt)
Return the fixed value specified when the timezone instance is constructed. The dt argument is ignored. The return value is a timedelta instance equal to the difference between the local time and UTC. Changed in version 3.7: The UTC offset is not restricted to a whole number of minutes.
timezone.tzname(dt)
Return the fixed value specified when the timezone instance is constructed. If name is not provided in the constructor, the name returned by tzname(dt) is generated from the value of the offset as follows. If offset is timedelta(0), the name is “UTC”, otherwise it is a string in the format UTC±HH:MM, where ± is the sign of offset, HH and MM are two digits of offset.hours and offset.minutes respectively. Changed in version 3.6: Name generated from offset=timedelta(0) is now plain ‘UTC’, not 'UTC+00:00'.
timezone.dst(dt)
Always returns None.
timezone.fromutc(dt)
Return dt + offset. The dt argument must be an aware datetime instance, with tzinfo set to self.
Class attributes:
timezone.utc
The UTC timezone, timezone(timedelta(0)).
strftime() and strptime() Behavior date, datetime, and time objects all support a strftime(format) method, to create a string representing the time under the control of an explicit format string. Conversely, the datetime.strptime() class method creates a datetime object from a string representing a date and time and a corresponding format string. The table below provides a high-level comparison of strftime() versus strptime():
strftime strptime
Usage Convert object to a string according to a given format Parse a string into a datetime object given a corresponding format
Type of method Instance method Class method
Method of date; datetime; time datetime
Signature strftime(format) strptime(date_string, format)
strftime() and strptime() Format Codes The following is a list of all the format codes that the 1989 C standard requires, and these work on all platforms with a standard C implementation.
Directive Meaning Example Notes
%a Weekday as locale’s abbreviated name. (1)
%A Weekday as locale’s full name. (1)
%w Weekday as a decimal number, where 0 is Sunday and 6 is Saturday. 0, 1, …, 6
%d Day of the month as a zero-padded decimal number. 01, 02, …, 31 (9)
%b Month as locale’s abbreviated name. (1)
%B Month as locale’s full name. (1)
%m Month as a zero-padded decimal number. 01, 02, …, 12 (9)
%y Year without century as a zero-padded decimal number. 00, 01, …, 99 (9)
%Y Year with century as a decimal number. 0001, 0002, …, 2013, 2014, …, 9998, 9999 (2)
%H Hour (24-hour clock) as a zero-padded decimal number. 00, 01, …, 23 (9)
%I Hour (12-hour clock) as a zero-padded decimal number. 01, 02, …, 12 (9)
%p Locale’s equivalent of either AM or PM. (1), (3)
%M Minute as a zero-padded decimal number. 00, 01, …, 59 (9)
%S Second as a zero-padded decimal number. 00, 01, …, 59 (4), (9)
%f Microsecond as a decimal number, zero-padded on the left. 000000, 000001, …, 999999 (5)
%z UTC offset in the form ±HHMM[SS[.ffffff]] (empty string if the object is naive). (empty), +0000, -0400, +1030, +063415, -030712.345216 (6)
%Z Time zone name (empty string if the object is naive). (empty), UTC, GMT (6)
%j Day of the year as a zero-padded decimal number. 001, 002, …, 366 (9)
%U Week number of the year (Sunday as the first day of the week) as a zero padded decimal number. All days in a new year preceding the first Sunday are considered to be in week 0. 00, 01, …, 53 (7), (9)
%W Week number of the year (Monday as the first day of the week) as a decimal number. All days in a new year preceding the first Monday are considered to be in week 0. 00, 01, …, 53 (7), (9)
%c Locale’s appropriate date and time representation. (1)
%x Locale’s appropriate date representation. (1)
%X Locale’s appropriate time representation. (1)
%% A literal '%' character. % Several additional directives not required by the C89 standard are included for convenience. These parameters all correspond to ISO 8601 date values.
Directive Meaning Example Notes
%G ISO 8601 year with century representing the year that contains the greater part of the ISO week (%V). 0001, 0002, …, 2013, 2014, …, 9998, 9999 (8)
%u ISO 8601 weekday as a decimal number where 1 is Monday. 1, 2, …, 7
%V ISO 8601 week as a decimal number with Monday as the first day of the week. Week 01 is the week containing Jan 4. 01, 02, …, 53 (8), (9) These may not be available on all platforms when used with the strftime() method. The ISO 8601 year and ISO 8601 week directives are not interchangeable with the year and week number directives above. Calling strptime() with incomplete or ambiguous ISO 8601 directives will raise a ValueError. The full set of format codes supported varies across platforms, because Python calls the platform C library’s strftime() function, and platform variations are common. To see the full set of format codes supported on your platform, consult the strftime(3) documentation. New in version 3.6: %G, %u and %V were added. Technical Detail Broadly speaking, d.strftime(fmt) acts like the time module’s time.strftime(fmt, d.timetuple()) although not all objects support a timetuple() method. For the datetime.strptime() class method, the default value is 1900-01-01T00:00:00.000: any components not specified in the format string will be pulled from the default value. 4 Using datetime.strptime(date_string, format) is equivalent to: datetime(*(time.strptime(date_string, format)[0:6]))
except when the format includes sub-second components or timezone offset information, which are supported in datetime.strptime but are discarded by time.strptime. For time objects, the format codes for year, month, and day should not be used, as time objects have no such values. If they’re used anyway, 1900 is substituted for the year, and 1 for the month and day. For date objects, the format codes for hours, minutes, seconds, and microseconds should not be used, as date objects have no such values. If they’re used anyway, 0 is substituted for them. For the same reason, handling of format strings containing Unicode code points that can’t be represented in the charset of the current locale is also platform-dependent. On some platforms such code points are preserved intact in the output, while on others strftime may raise UnicodeError or return an empty string instead. Notes: Because the format depends on the current locale, care should be taken when making assumptions about the output value. Field orderings will vary (for example, “month/day/year” versus “day/month/year”), and the output may contain Unicode characters encoded using the locale’s default encoding (for example, if the current locale is ja_JP, the default encoding could be any one of eucJP, SJIS, or utf-8; use locale.getlocale() to determine the current locale’s encoding).
The strptime() method can parse years in the full [1, 9999] range, but years < 1000 must be zero-filled to 4-digit width. Changed in version 3.2: In previous versions, strftime() method was restricted to years >= 1900. Changed in version 3.3: In version 3.2, strftime() method was restricted to years >= 1000. When used with the strptime() method, the %p directive only affects the output hour field if the %I directive is used to parse the hour. Unlike the time module, the datetime module does not support leap seconds. When used with the strptime() method, the %f directive accepts from one to six digits and zero pads on the right. %f is an extension to the set of format characters in the C standard (but implemented separately in datetime objects, and therefore always available).
For a naive object, the %z and %Z format codes are replaced by empty strings. For an aware object:
%z
utcoffset() is transformed into a string of the form ±HHMM[SS[.ffffff]], where HH is a 2-digit string giving the number of UTC offset hours, MM is a 2-digit string giving the number of UTC offset minutes, SS is a 2-digit string giving the number of UTC offset seconds and ffffff is a 6-digit string giving the number of UTC offset microseconds. The ffffff part is omitted when the offset is a whole number of seconds and both the ffffff and the SS part is omitted when the offset is a whole number of minutes. For example, if utcoffset() returns timedelta(hours=-3, minutes=-30), %z is replaced with the string '-0330'. Changed in version 3.7: The UTC offset is not restricted to a whole number of minutes. Changed in version 3.7: When the %z directive is provided to the strptime() method, the UTC offsets can have a colon as a separator between hours, minutes and seconds. For example, '+01:00:00' will be parsed as an offset of one hour. In addition, providing 'Z' is identical to '+00:00'.
%Z
In strftime(), %Z is replaced by an empty string if tzname() returns None; otherwise %Z is replaced by the returned value, which must be a string. strptime() only accepts certain values for %Z: any value in time.tzname for your machine’s locale the hard-coded values UTC and GMT
So someone living in Japan may have JST, UTC, and GMT as valid values, but probably not EST. It will raise ValueError for invalid values. Changed in version 3.2: When the %z directive is provided to the strptime() method, an aware datetime object will be produced. The tzinfo of the result will be set to a timezone instance. When used with the strptime() method, %U and %W are only used in calculations when the day of the week and the calendar year (%Y) are specified. Similar to %U and %W, %V is only used in calculations when the day of the week and the ISO year (%G) are specified in a strptime() format string. Also note that %G and %Y are not interchangeable. When used with the strptime() method, the leading zero is optional for formats %d, %m, %H, %I, %M, %S, %J, %U, %W, and %V. Format %y does require a leading zero. Footnotes
1
If, that is, we ignore the effects of Relativity
2
This matches the definition of the “proleptic Gregorian” calendar in Dershowitz and Reingold’s book Calendrical Calculations, where it’s the base calendar for all computations. See the book for algorithms for converting between proleptic Gregorian ordinals and many other calendar systems.
3
See R. H. van Gent’s guide to the mathematics of the ISO 8601 calendar for a good explanation.
4
Passing datetime.strptime('Feb 29', '%b %d') will fail since 1900 is not a leap year. | python.library.datetime |
class datetime.date(year, month, day)
All arguments are required. Arguments must be integers, in the following ranges: MINYEAR <= year <= MAXYEAR 1 <= month <= 12 1 <= day <= number of days in the given month and year If an argument outside those ranges is given, ValueError is raised. | python.library.datetime#datetime.date |
date.ctime()
Return a string representing the date: >>> from datetime import date
>>> date(2002, 12, 4).ctime()
'Wed Dec 4 00:00:00 2002'
d.ctime() is equivalent to: time.ctime(time.mktime(d.timetuple()))
on platforms where the native C ctime() function (which time.ctime() invokes, but which date.ctime() does not invoke) conforms to the C standard. | python.library.datetime#datetime.date.ctime |
date.day
Between 1 and the number of days in the given month of the given year. | python.library.datetime#datetime.date.day |
classmethod date.fromisocalendar(year, week, day)
Return a date corresponding to the ISO calendar date specified by year, week and day. This is the inverse of the function date.isocalendar(). New in version 3.8. | python.library.datetime#datetime.date.fromisocalendar |
classmethod date.fromisoformat(date_string)
Return a date corresponding to a date_string given in the format YYYY-MM-DD: >>> from datetime import date
>>> date.fromisoformat('2019-12-04')
datetime.date(2019, 12, 4)
This is the inverse of date.isoformat(). It only supports the format YYYY-MM-DD. New in version 3.7. | python.library.datetime#datetime.date.fromisoformat |
classmethod date.fromordinal(ordinal)
Return the date corresponding to the proleptic Gregorian ordinal, where January 1 of year 1 has ordinal 1. ValueError is raised unless 1 <= ordinal <=
date.max.toordinal(). For any date d, date.fromordinal(d.toordinal()) == d. | python.library.datetime#datetime.date.fromordinal |
classmethod date.fromtimestamp(timestamp)
Return the local date corresponding to the POSIX timestamp, such as is returned by time.time(). This may raise OverflowError, if the timestamp is out of the range of values supported by the platform C localtime() function, and OSError on localtime() failure. It’s common for this to be restricted to years from 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by fromtimestamp(). Changed in version 3.3: Raise OverflowError instead of ValueError if the timestamp is out of the range of values supported by the platform C localtime() function. Raise OSError instead of ValueError on localtime() failure. | python.library.datetime#datetime.date.fromtimestamp |
date.isocalendar()
Return a named tuple object with three components: year, week and weekday. The ISO calendar is a widely used variant of the Gregorian calendar. 3 The ISO year consists of 52 or 53 full weeks, and where a week starts on a Monday and ends on a Sunday. The first week of an ISO year is the first (Gregorian) calendar week of a year containing a Thursday. This is called week number 1, and the ISO year of that Thursday is the same as its Gregorian year. For example, 2004 begins on a Thursday, so the first week of ISO year 2004 begins on Monday, 29 Dec 2003 and ends on Sunday, 4 Jan 2004: >>> from datetime import date
>>> date(2003, 12, 29).isocalendar()
datetime.IsoCalendarDate(year=2004, week=1, weekday=1)
>>> date(2004, 1, 4).isocalendar()
datetime.IsoCalendarDate(year=2004, week=1, weekday=7)
Changed in version 3.9: Result changed from a tuple to a named tuple. | python.library.datetime#datetime.date.isocalendar |
date.isoformat()
Return a string representing the date in ISO 8601 format, YYYY-MM-DD: >>> from datetime import date
>>> date(2002, 12, 4).isoformat()
'2002-12-04'
This is the inverse of date.fromisoformat(). | python.library.datetime#datetime.date.isoformat |
date.isoweekday()
Return the day of the week as an integer, where Monday is 1 and Sunday is 7. For example, date(2002, 12, 4).isoweekday() == 3, a Wednesday. See also weekday(), isocalendar(). | python.library.datetime#datetime.date.isoweekday |
date.max
The latest representable date, date(MAXYEAR, 12, 31). | python.library.datetime#datetime.date.max |
date.min
The earliest representable date, date(MINYEAR, 1, 1). | python.library.datetime#datetime.date.min |
date.month
Between 1 and 12 inclusive. | python.library.datetime#datetime.date.month |
date.replace(year=self.year, month=self.month, day=self.day)
Return a date with the same value, except for those parameters given new values by whichever keyword arguments are specified. Example: >>> from datetime import date
>>> d = date(2002, 12, 31)
>>> d.replace(day=26)
datetime.date(2002, 12, 26) | python.library.datetime#datetime.date.replace |
date.resolution
The smallest possible difference between non-equal date objects, timedelta(days=1). | python.library.datetime#datetime.date.resolution |
date.strftime(format)
Return a string representing the date, controlled by an explicit format string. Format codes referring to hours, minutes or seconds will see 0 values. For a complete list of formatting directives, see strftime() and strptime() Behavior. | python.library.datetime#datetime.date.strftime |
date.timetuple()
Return a time.struct_time such as returned by time.localtime(). The hours, minutes and seconds are 0, and the DST flag is -1. d.timetuple() is equivalent to: time.struct_time((d.year, d.month, d.day, 0, 0, 0, d.weekday(), yday, -1))
where yday = d.toordinal() - date(d.year, 1, 1).toordinal() + 1 is the day number within the current year starting with 1 for January 1st. | python.library.datetime#datetime.date.timetuple |
classmethod date.today()
Return the current local date. This is equivalent to date.fromtimestamp(time.time()). | python.library.datetime#datetime.date.today |
date.toordinal()
Return the proleptic Gregorian ordinal of the date, where January 1 of year 1 has ordinal 1. For any date object d, date.fromordinal(d.toordinal()) == d. | python.library.datetime#datetime.date.toordinal |
date.weekday()
Return the day of the week as an integer, where Monday is 0 and Sunday is 6. For example, date(2002, 12, 4).weekday() == 2, a Wednesday. See also isoweekday(). | python.library.datetime#datetime.date.weekday |
date.year
Between MINYEAR and MAXYEAR inclusive. | python.library.datetime#datetime.date.year |
date.__format__(format)
Same as date.strftime(). This makes it possible to specify a format string for a date object in formatted string literals and when using str.format(). For a complete list of formatting directives, see strftime() and strptime() Behavior. | python.library.datetime#datetime.date.__format__ |
date.__str__()
For a date d, str(d) is equivalent to d.isoformat(). | python.library.datetime#datetime.date.__str__ |
class datetime.datetime(year, month, day, hour=0, minute=0, second=0, microsecond=0, tzinfo=None, *, fold=0)
The year, month and day arguments are required. tzinfo may be None, or an instance of a tzinfo subclass. The remaining arguments must be integers in the following ranges:
MINYEAR <= year <= MAXYEAR,
1 <= month <= 12,
1 <= day <= number of days in the given month and year,
0 <= hour < 24,
0 <= minute < 60,
0 <= second < 60,
0 <= microsecond < 1000000,
fold in [0, 1]. If an argument outside those ranges is given, ValueError is raised. New in version 3.6: Added the fold argument. | python.library.datetime#datetime.datetime |
datetime.astimezone(tz=None)
Return a datetime object with new tzinfo attribute tz, adjusting the date and time data so the result is the same UTC time as self, but in tz’s local time. If provided, tz must be an instance of a tzinfo subclass, and its utcoffset() and dst() methods must not return None. If self is naive, it is presumed to represent time in the system timezone. If called without arguments (or with tz=None) the system local timezone is assumed for the target timezone. The .tzinfo attribute of the converted datetime instance will be set to an instance of timezone with the zone name and offset obtained from the OS. If self.tzinfo is tz, self.astimezone(tz) is equal to self: no adjustment of date or time data is performed. Else the result is local time in the timezone tz, representing the same UTC time as self: after astz = dt.astimezone(tz), astz - astz.utcoffset() will have the same date and time data as dt - dt.utcoffset(). If you merely want to attach a time zone object tz to a datetime dt without adjustment of date and time data, use dt.replace(tzinfo=tz). If you merely want to remove the time zone object from an aware datetime dt without conversion of date and time data, use dt.replace(tzinfo=None). Note that the default tzinfo.fromutc() method can be overridden in a tzinfo subclass to affect the result returned by astimezone(). Ignoring error cases, astimezone() acts like: def astimezone(self, tz):
if self.tzinfo is tz:
return self
# Convert self to UTC, and attach the new time zone object.
utc = (self - self.utcoffset()).replace(tzinfo=tz)
# Convert from UTC to tz's local time.
return tz.fromutc(utc)
Changed in version 3.3: tz now can be omitted. Changed in version 3.6: The astimezone() method can now be called on naive instances that are presumed to represent system local time. | python.library.datetime#datetime.datetime.astimezone |
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