docopt
Pythonic argument parser, that will make you smile
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Description
``docopt`` creates *beautiful* command-line interfaces
======================================================================
Video introduction to **docopt**: `PyCon UK 2012: Create *beautiful*
command-line interfaces with Python <http://youtu.be/pXhcPJK5cMc>`_
New in version 0.6.1:
- Fix issue `#85 <https://github.com/docopt/docopt/issues/85>`_
which caused improper handling of ``[options]`` shortcut
if it was present several times.
New in version 0.6.0:
- New argument ``options_first``, disallows interspersing options
and arguments. If you supply ``options_first=True`` to
``docopt``, it will interpret all arguments as positional
arguments after first positional argument.
- If option with argument could be repeated, its default value
will be interpreted as space-separated list. E.g. with
``[default: ./here ./there]`` will be interpreted as
``['./here', './there']``.
Breaking changes:
- Meaning of ``[options]`` shortcut slightly changed. Previously
it ment *"any known option"*. Now it means *"any option not in
usage-pattern"*. This avoids the situation when an option is
allowed to be repeated unintentionaly.
- ``argv`` is ``None`` by default, not ``sys.argv[1:]``.
This allows ``docopt`` to always use the *latest* ``sys.argv``,
not ``sys.argv`` during import time.
Isn't it awesome how ``optparse`` and ``argparse`` generate help
messages based on your code?!
*Hell no!* You know what's awesome? It's when the option parser *is*
generated based on the beautiful help message that you write yourself!
This way you don't need to write this stupid repeatable parser-code,
and instead can write only the help message--*the way you want it*.
**docopt** helps you create most beautiful command-line interfaces
*easily*:
.. code:: python
"""Naval Fate.
Usage:
naval_fate.py ship new <name>...
naval_fate.py ship <name> move <x> <y> [--speed=<kn>]
naval_fate.py ship shoot <x> <y>
naval_fate.py mine (set|remove) <x> <y> [--moored | --drifting]
naval_fate.py (-h | --help)
naval_fate.py --version
Options:
-h --help Show this screen.
--version Show version.
--speed=<kn> Speed in knots [default: 10].
--moored Moored (anchored) mine.
--drifting Drifting mine.
"""
from docopt import docopt
if __name__ == '__main__':
arguments = docopt(__doc__, version='Naval Fate 2.0')
print(arguments)
Beat that! The option parser is generated based on the docstring above
that is passed to ``docopt`` function. ``docopt`` parses the usage
pattern (``"Usage: ..."``) and option descriptions (lines starting
with dash "``-``") and ensures that the program invocation matches the
usage pattern; it parses options, arguments and commands based on
that. The basic idea is that *a good help message has all necessary
information in it to make a parser*.
Also, `PEP 257 <http://www.python.org/dev/peps/pep-0257/>`_ recommends
putting help message in the module docstrings.
Installation
======================================================================
Use `pip <http://pip-installer.org>`_ or easy_install::
pip install docopt==0.6.2
Alternatively, you can just drop ``docopt.py`` file into your
project--it is self-contained.
**docopt** is tested with Python 2.5, 2.6, 2.7, 3.2, 3.3 and PyPy.
API
======================================================================
.. code:: python
from docopt import docopt
.. code:: python
docopt(doc, argv=None, help=True, version=None, options_first=False)
``docopt`` takes 1 required and 4 optional arguments:
- ``doc`` could be a module docstring (``__doc__``) or some other
string that contains a **help message** that will be parsed to
create the option parser. The simple rules of how to write such a
help message are given in next sections. Here is a quick example of
such a string:
.. code:: python
"""Usage: my_program.py [-hso FILE] [--quiet | --verbose] [INPUT ...]
-h --help show this
-s --sorted sorted output
-o FILE specify output file [default: ./test.txt]
--quiet print less text
--verbose print more text
"""
- ``argv`` is an optional argument vector; by default ``docopt`` uses
the argument vector passed to your program (``sys.argv[1:]``).
Alternatively you can supply a list of strings like ``['--verbose',
'-o', 'hai.txt']``.
- ``help``, by default ``True``, specifies whether the parser should
automatically print the help message (supplied as ``doc``) and
terminate, in case ``-h`` or ``--help`` option is encountered
(options should exist in usage pattern, more on that below). If you
want to handle ``-h`` or ``--help`` options manually (as other
options), set ``help=False``.
- ``version``, by default ``None``, is an optional argument that
specifies the version of your program. If supplied, then, (assuming
``--version`` option is mentioned in usage pattern) when parser
encounters the ``--version`` option, it will print the supplied
version and terminate. ``version`` could be any printable object,
but most likely a string, e.g. ``"2.1.0rc1"``.
Note, when ``docopt`` is set to automatically handle ``-h``,
``--help`` and ``--version`` options, you still need to mention
them in usage pattern for this to work. Also, for your users to
know about them.
- ``options_first``, by default ``False``. If set to ``True`` will
disallow mixing options and positional argument. I.e. after first
positional argument, all arguments will be interpreted as positional
even if the look like options. This can be used for strict
compatibility with POSIX, or if you want to dispatch your arguments
to other programs.
The **return** value is a simple dictionary with options, arguments
and commands as keys, spelled exactly like in your help message. Long
versions of options are given priority. For example, if you invoke the
top example as::
naval_fate.py ship Guardian move 100 150 --speed=15
the return dictionary will be:
.. code:: python
{'--drifting': False, 'mine': False,
'--help': False, 'move': True,
'--moored': False, 'new': False,
'--speed': '15', 'remove': False,
'--version': False, 'set': False,
'<name>': ['Guardian'], 'ship': True,
'<x>': '100', 'shoot': False,
'<y>': '150'}
Help message format
======================================================================
Help message consists of 2 parts:
- Usage pattern, e.g.::
Usage: my_program.py [-hso FILE] [--quiet | --verbose] [INPUT ...]
- Option descriptions, e.g.::
-h --help show this
-s --sorted sorted output
-o FILE specify output file [default: ./test.txt]
--quiet print less text
--verbose print more text
Their format is described below; other text is ignored.
Usage pattern format
----------------------------------------------------------------------
**Usage pattern** is a substring of ``doc`` that starts with
``usage:`` (case *insensitive*) and ends with a *visibly* empty line.
Minimum example:
.. code:: python
"""Usage: my_program.py
"""
The first word after ``usage:`` is interpreted as your program's name.
You can specify your program's name several times to signify several
exclusive patterns:
.. code:: python
"""Usage: my_program.py FILE
my_program.py COUNT FILE
"""
Each pattern can consist of the following elements:
- **<arguments>**, **ARGUMENTS**. Arguments are specified as either
upper-case words, e.g. ``my_program.py CONTENT-PATH`` or words
surrounded by angular brackets: ``my_program.py <content-path>``.
- **--options**. Options are words started with dash (``-``), e.g.
``--output``, ``-o``. You can "stack" several of one-letter
options, e.g. ``-oiv`` which will be the same as ``-o -i -v``. The
options can have arguments, e.g. ``--input=FILE`` or ``-i FILE`` or
even ``-iFILE``. However it is important that you specify option
descriptions if you want for option to have an argument, a default
value, or specify synonymous short/long versions of option (see next
section on option descriptions).
- **commands** are words that do *not* follow the described above
conventions of ``--options`` or ``<arguments>`` or ``ARGUMENTS``,
plus two special commands: dash "``-``" and double dash "``--``"
(see below).
Use the following constructs to specify patterns:
- **[ ]** (brackets) **optional** elements. e.g.: ``my_program.py
[-hvqo FILE]``
- **( )** (parens) **required** elements. All elements that are *not*
put in **[ ]** are also required, e.g.: ``my_program.py
--path=<path> <file>...`` is the same as ``my_program.py
(--path=<path> <file>...)``. (Note, "required options" might be not
a good idea for your users).
- **|** (pipe) **mutualy exclusive** elements. Group them using **(
)** if one of the mutually exclusive elements is required:
``my_program.py (--clockwise | --counter-clockwise) TIME``. Group
them using **[ ]** if none of the mutually-exclusive elements are
required: ``my_program.py [--left | --right]``.
- **...** (ellipsis) **one or more** elements. To specify that
arbitrary number of repeating elements could be accepted, use
ellipsis (``...``), e.g. ``my_program.py FILE ...`` means one or
more ``FILE``-s are accepted. If you want to accept zero or more
elements, use brackets, e.g.: ``my_program.py [FILE ...]``. Ellipsis
works as a unary operator on the expression to the left.
- **[options]** (case sensitive) shortcut for any options. You can
use it if you want to specify that the usage pattern could be
provided with any options defined below in the option-descriptions
and do not want to enumerate them all in usage-pattern. -
"``[--]``". Double dash "``--`