| | |
| | |
| |
|
| | """Abstract Base Classes (ABCs) according to PEP 3119.""" |
| |
|
| |
|
| | def abstractmethod(funcobj): |
| | """A decorator indicating abstract methods. |
| | |
| | Requires that the metaclass is ABCMeta or derived from it. A |
| | class that has a metaclass derived from ABCMeta cannot be |
| | instantiated unless all of its abstract methods are overridden. |
| | The abstract methods can be called using any of the normal |
| | 'super' call mechanisms. abstractmethod() may be used to declare |
| | abstract methods for properties and descriptors. |
| | |
| | Usage: |
| | |
| | class C(metaclass=ABCMeta): |
| | @abstractmethod |
| | def my_abstract_method(self, ...): |
| | ... |
| | """ |
| | funcobj.__isabstractmethod__ = True |
| | return funcobj |
| |
|
| |
|
| | class abstractclassmethod(classmethod): |
| | """A decorator indicating abstract classmethods. |
| | |
| | Deprecated, use 'classmethod' with 'abstractmethod' instead: |
| | |
| | class C(ABC): |
| | @classmethod |
| | @abstractmethod |
| | def my_abstract_classmethod(cls, ...): |
| | ... |
| | |
| | """ |
| |
|
| | __isabstractmethod__ = True |
| |
|
| | def __init__(self, callable): |
| | callable.__isabstractmethod__ = True |
| | super().__init__(callable) |
| |
|
| |
|
| | class abstractstaticmethod(staticmethod): |
| | """A decorator indicating abstract staticmethods. |
| | |
| | Deprecated, use 'staticmethod' with 'abstractmethod' instead: |
| | |
| | class C(ABC): |
| | @staticmethod |
| | @abstractmethod |
| | def my_abstract_staticmethod(...): |
| | ... |
| | |
| | """ |
| |
|
| | __isabstractmethod__ = True |
| |
|
| | def __init__(self, callable): |
| | callable.__isabstractmethod__ = True |
| | super().__init__(callable) |
| |
|
| |
|
| | class abstractproperty(property): |
| | """A decorator indicating abstract properties. |
| | |
| | Deprecated, use 'property' with 'abstractmethod' instead: |
| | |
| | class C(ABC): |
| | @property |
| | @abstractmethod |
| | def my_abstract_property(self): |
| | ... |
| | |
| | """ |
| |
|
| | __isabstractmethod__ = True |
| |
|
| |
|
| | try: |
| | from _abc import (get_cache_token, _abc_init, _abc_register, |
| | _abc_instancecheck, _abc_subclasscheck, _get_dump, |
| | _reset_registry, _reset_caches) |
| | except ImportError: |
| | from _py_abc import ABCMeta, get_cache_token |
| | ABCMeta.__module__ = 'abc' |
| | else: |
| | class ABCMeta(type): |
| | """Metaclass for defining Abstract Base Classes (ABCs). |
| | |
| | Use this metaclass to create an ABC. An ABC can be subclassed |
| | directly, and then acts as a mix-in class. You can also register |
| | unrelated concrete classes (even built-in classes) and unrelated |
| | ABCs as 'virtual subclasses' -- these and their descendants will |
| | be considered subclasses of the registering ABC by the built-in |
| | issubclass() function, but the registering ABC won't show up in |
| | their MRO (Method Resolution Order) nor will method |
| | implementations defined by the registering ABC be callable (not |
| | even via super()). |
| | """ |
| | def __new__(mcls, name, bases, namespace, **kwargs): |
| | cls = super().__new__(mcls, name, bases, namespace, **kwargs) |
| | _abc_init(cls) |
| | return cls |
| |
|
| | def register(cls, subclass): |
| | """Register a virtual subclass of an ABC. |
| | |
| | Returns the subclass, to allow usage as a class decorator. |
| | """ |
| | return _abc_register(cls, subclass) |
| |
|
| | def __instancecheck__(cls, instance): |
| | """Override for isinstance(instance, cls).""" |
| | return _abc_instancecheck(cls, instance) |
| |
|
| | def __subclasscheck__(cls, subclass): |
| | """Override for issubclass(subclass, cls).""" |
| | return _abc_subclasscheck(cls, subclass) |
| |
|
| | def _dump_registry(cls, file=None): |
| | """Debug helper to print the ABC registry.""" |
| | print(f"Class: {cls.__module__}.{cls.__qualname__}", file=file) |
| | print(f"Inv. counter: {get_cache_token()}", file=file) |
| | (_abc_registry, _abc_cache, _abc_negative_cache, |
| | _abc_negative_cache_version) = _get_dump(cls) |
| | print(f"_abc_registry: {_abc_registry!r}", file=file) |
| | print(f"_abc_cache: {_abc_cache!r}", file=file) |
| | print(f"_abc_negative_cache: {_abc_negative_cache!r}", file=file) |
| | print(f"_abc_negative_cache_version: {_abc_negative_cache_version!r}", |
| | file=file) |
| |
|
| | def _abc_registry_clear(cls): |
| | """Clear the registry (for debugging or testing).""" |
| | _reset_registry(cls) |
| |
|
| | def _abc_caches_clear(cls): |
| | """Clear the caches (for debugging or testing).""" |
| | _reset_caches(cls) |
| |
|
| |
|
| | def update_abstractmethods(cls): |
| | """Recalculate the set of abstract methods of an abstract class. |
| | |
| | If a class has had one of its abstract methods implemented after the |
| | class was created, the method will not be considered implemented until |
| | this function is called. Alternatively, if a new abstract method has been |
| | added to the class, it will only be considered an abstract method of the |
| | class after this function is called. |
| | |
| | This function should be called before any use is made of the class, |
| | usually in class decorators that add methods to the subject class. |
| | |
| | Returns cls, to allow usage as a class decorator. |
| | |
| | If cls is not an instance of ABCMeta, does nothing. |
| | """ |
| | if not hasattr(cls, '__abstractmethods__'): |
| | |
| | |
| | |
| | return cls |
| |
|
| | abstracts = set() |
| | |
| | |
| | for scls in cls.__bases__: |
| | for name in getattr(scls, '__abstractmethods__', ()): |
| | value = getattr(cls, name, None) |
| | if getattr(value, "__isabstractmethod__", False): |
| | abstracts.add(name) |
| | |
| | for name, value in cls.__dict__.items(): |
| | if getattr(value, "__isabstractmethod__", False): |
| | abstracts.add(name) |
| | cls.__abstractmethods__ = frozenset(abstracts) |
| | return cls |
| |
|
| |
|
| | class ABC(metaclass=ABCMeta): |
| | """Helper class that provides a standard way to create an ABC using |
| | inheritance. |
| | """ |
| | __slots__ = () |
| |
|