blessed/docs/intro.rst

| |pypi_downloads| |codecov| |windows| |linux| |mac| |bsd|

Introduction
============

Blessed is an easy, practical *library* for making *terminal* apps, by providing an elegant,
well-documented interface to Colors_, Keyboard_ input, and screen position and Location_
capabilities.

.. code-block:: python

    from blessed import Terminal

    term = Terminal()

    print(term.home + term.clear + term.move_y(term.height // 2))
    print(term.black_on_darkkhaki(term.center('press any key to continue.')))

    with term.cbreak(), term.hidden_cursor():
        inp = term.inkey()

    print(term.move_down(2) + 'You pressed ' + term.bold(repr(inp)))

.. figure:: https://dxtz6bzwq9sxx.cloudfront.net/demo_basic_intro.gif
   :alt: Animation of running the code example

It's meant to be *fun* and *easy*, to do basic terminal graphics and styling with Python using
*blessed*. Terminal_ is the only class you need to import and the only object you should need for
Terminal capabilities.

Whether you want to improve CLI apps with colors, or make fullscreen applications or games,
*blessed* should help get you started quickly. Your users will love it because it works on Windows,
Mac, and Linux, and you will love it because it has plenty of documentation and examples!

Full documentation at https://blessed.readthedocs.io/en/latest/

Examples
--------

.. figure:: https://dxtz6bzwq9sxx.cloudfront.net/blessed_demo_intro.gif
   :alt: Animations of x11-colorpicker.py, bounce.py, worms.py, and plasma.py

   x11-colorpicker.py_, bounce.py_, worms.py_, and plasma.py_, from our repository.

Exemplary 3rd-party examples which use *blessed*,

.. figure:: https://dxtz6bzwq9sxx.cloudfront.net/demo_3rdparty_voltron.png
   :alt: Screenshot of 'Voltron' (By the author of Voltron, from their README).

   Voltron_ is an extensible debugger UI toolkit written in Python

.. figure:: https://dxtz6bzwq9sxx.cloudfront.net/demo_3rdparty_cursewords.gif
   :alt: Animation of 'cursewords' (By the author of cursewords, from their README).

   cursewords_ is "graphical" command line program for solving crossword puzzles in the terminal.

.. figure:: https://dxtz6bzwq9sxx.cloudfront.net/demo_3rdparty_githeat.gif
   :alt: Animation of 'githeat.interactive', using blessed repository at the time of capture.

   GitHeat_ builds an interactive heatmap of git history.

.. figure:: https://dxtz6bzwq9sxx.cloudfront.net/demo_3rdparty_dashing.gif
   :alt: Animations from 'Dashing' (By the author of Dashing, from their README)

   Dashing_ is a library to quickly create terminal-based dashboards.

.. figure:: https://dxtz6bzwq9sxx.cloudfront.net/demo_3rdparty_enlighten.gif
   :alt: Animations from 'Enlighten' (By the author of Enlighten, from their README)

   Enlighten_ is a console progress bar library that allows simultaneous output without redirection.

.. figure:: https://dxtz6bzwq9sxx.cloudfront.net/blessed_3rdparty_macht.gif
   :alt: Demonstration of 'macht', a 2048 clone

   macht_ is a clone of the (briefly popular) puzzle game, 2048.

Requirements
------------

*Blessed* works with Windows, Mac, Linux, and BSD's, on Python 2.7, 3.5+.

Brief Overview
--------------

*Blessed* is more than just a Python wrapper around curses_:

* Styles_, Colors_, and maybe a little positioning without necessarily clearing the whole screen
  first.
* Works great with Python's new f-strings_ or any other kind of string formatting.
* Provides up-to-the-moment Location_ and terminal height and width, so you can respond to terminal
  size changes.
* Avoids making a mess if the output gets piped to a non-terminal, you can output sequences to any
  file-like object such as *StringIO*, files, pipes or sockets.
* Uses `terminfo(5)`_ so it works with any terminal type and capability: No more C-like calls to
  tigetstr_ and tparm_.
* Non-obtrusive calls to only the capabilities database ensures that you are free to mix and match
  with calls to any other curses application code or library you like.
* Provides context managers `Terminal.fullscreen()`_ and `Terminal.hidden_cursor()`_ to safely
  express terminal modes, curses development will no longer fudge up your shell.
* Act intelligently when somebody redirects your output to a file, omitting all of the special
  sequences colors, but still containing all of the text.

*Blessed* is a fork of `blessings <https://github.com/erikrose/blessings>`_, which does all of
the same above with the same API, as well as following **enhancements**:

* Windows support, new since Dec. 2019!
* Dead-simple keyboard handling: safely decoding unicode input in your system's preferred locale and
  supports application/arrow keys.
* 24-bit color support, using `Terminal.color_rgb()`_ and `Terminal.on_color_rgb()`_ and all X11
  Colors_ by name, and not by number.
* Determine cursor location using `Terminal.get_location()`_, enter key-at-a-time input mode using
  `Terminal.cbreak()`_ or `Terminal.raw()`_ context managers, and read timed key presses using
  `Terminal.inkey()`_.
* Allows the *printable length* of strings that contain sequences to be determined by
  `Terminal.length()`_, supporting additional methods `Terminal.wrap()`_ and `Terminal.center()`_,
  terminal-aware variants of the built-in function `textwrap.wrap()`_ and method `str.center()`_,
  respectively.
* Allows sequences to be removed from strings that contain them, using `Terminal.strip_seqs()`_ or
  sequences and whitespace using `Terminal.strip()`_.

Before And After
----------------

With the built-in curses_ module, this is how you would typically
print some underlined text at the bottom of the screen:

.. code-block:: python

    from curses import tigetstr, setupterm, tparm
    from fcntl import ioctl
    from os import isatty
    import struct
    import sys
    from termios import TIOCGWINSZ

    # If we want to tolerate having our output piped to other commands or
    # files without crashing, we need to do all this branching:
    if hasattr(sys.stdout, 'fileno') and isatty(sys.stdout.fileno()):
        setupterm()
        sc = tigetstr('sc')
        cup = tigetstr('cup')
        rc = tigetstr('rc')
        underline = tigetstr('smul')
        normal = tigetstr('sgr0')
    else:
        sc = cup = rc = underline = normal = ''

    # Save cursor position.
    print(sc)

    if cup:
        # tigetnum('lines') doesn't always update promptly, hence this:
        height = struct.unpack('hhhh', ioctl(0, TIOCGWINSZ, '\000' * 8))[0]

        # Move cursor to bottom.
        print(tparm(cup, height - 1, 0))

    print('This is {under}underlined{normal}!'
          .format(under=underline, normal=normal))

    # Restore cursor position.
    print(rc)

The same program with *Blessed* is simply:

.. code-block:: python

    from blessed import Terminal

    term = Terminal()
    with term.location(0, term.height - 1):
        print('This is ' + term.underline('underlined') + '!', end='')

.. _curses: https://docs.python.org/3/library/curses.html
.. _tigetstr: http://man.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man3/tigetstr.3
.. _tparm: http://man.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man3/tparm.3
.. _`terminfo(5)`: https://invisible-island.net/ncurses/man/terminfo.5.html
.. _str.center(): https://docs.python.org/3/library/stdtypes.html#str.center
.. _textwrap.wrap(): https://docs.python.org/3/library/textwrap.html#textwrap.wrap
.. _Terminal: https://blessed.readthedocs.io/en/stable/terminal.html
.. _`Terminal.fullscreen()`: https://blessed.readthedocs.io/en/latest/api/terminal.html#blessed.terminal.Terminal.fullscreen
.. _`Terminal.get_location()`: https://blessed.readthedocs.io/en/latest/location.html#finding-the-cursor
.. _`Terminal.color_rgb()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.color_rgb
.. _`Terminal.hidden_cursor()`: https://blessed.readthedocs.io/en/latest/api/terminal.html#blessed.terminal.Terminal.hidden_cursor
.. _`Terminal.on_color_rgb()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.on_color_rgb
.. _`Terminal.length()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.length
.. _`Terminal.strip()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.strip
.. _`Terminal.rstrip()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.rstrip
.. _`Terminal.lstrip()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.lstrip
.. _`Terminal.strip_seqs()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.strip_seqs
.. _`Terminal.wrap()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.wrap
.. _`Terminal.center()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.center
.. _`Terminal.rjust()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.rjust
.. _`Terminal.ljust()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.ljust
.. _`Terminal.cbreak()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.cbreak
.. _`Terminal.raw()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.raw
.. _`Terminal.inkey()`: https://blessed.readthedocs.io/en/stable/api/terminal.html#blessed.terminal.Terminal.inkey
.. _Colors: https://blessed.readthedocs.io/en/stable/colors.html
.. _Styles: https://blessed.readthedocs.io/en/stable/terminal.html#styles
.. _Location: https://blessed.readthedocs.io/en/stable/location.html
.. _Keyboard: https://blessed.readthedocs.io/en/stable/keyboard.html
.. _Examples: https://blessed.readthedocs.io/en/stable/examples.html
.. _x11-colorpicker.py: https://blessed.readthedocs.io/en/stable/examples.html#x11-colorpicker-py
.. _bounce.py: https://blessed.readthedocs.io/en/stable/examples.html#bounce-py
.. _worms.py: https://blessed.readthedocs.io/en/stable/examples.html#worms-py
.. _plasma.py: https://blessed.readthedocs.io/en/stable/examples.html#plasma-py
.. _Voltron: https://github.com/snare/voltron
.. _cursewords: https://github.com/thisisparker/cursewords
.. _GitHeat: https://github.com/AmmsA/Githeat
.. _Dashing: https://github.com/FedericoCeratto/dashing
.. _Enlighten: https://github.com/Rockhopper-Technologies/enlighten
.. _macht: https://github.com/rolfmorel/macht
.. _f-strings: https://docs.python.org/3/reference/lexical_analysis.html#f-strings
.. |pypi_downloads| image:: https://img.shields.io/pypi/dm/blessed.svg?logo=pypi
    :alt: Downloads
    :target: https://pypi.org/project/blessed/
.. |codecov| image:: https://codecov.io/gh/jquast/blessed/branch/master/graph/badge.svg
    :alt: codecov.io Code Coverage
    :target: https://codecov.io/gh/jquast/blessed/
.. |linux| image:: https://img.shields.io/badge/Linux-yes-success?logo=linux
    :alt: Linux supported
.. |windows| image:: https://img.shields.io/badge/Windows-yes-success?logo=windows
    :alt: Windows supported
.. |mac| image:: https://img.shields.io/badge/MacOS-yes-success?logo=apple
    :alt: MacOS supported
.. |bsd| image:: https://img.shields.io/badge/BSD-yes-success?logo=freebsd
    :alt: BSD supported