docopt 0.6.2
Pythonic argument parser, that will make you smile
License: MIT
Keywords: option arguments parsing optparse argparse getopt

``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 "``--``" is used by convention to separate
  positional arguments that can be mistaken for options. In order to
  support this convention add "``[--]``" to you usage patterns.  -
  "``[-]``". Single dash "``-``" is used by convention to signify that
  ``stdin`` is used instead of a file. To support this add "``[-]``"
  to you usage patterns. "``-``" act as a normal command.

If your pattern allows to match argument-less option (a flag) several
times::

    Usage: my_program.py [-v | -vv | -vvv]

then number of occurences of the option will be counted. I.e.
``args['-v']`` will be ``2`` if program was invoked as ``my_program
-vv``. Same works for commands.

If your usage patterns allows to match same-named option with argument
or positional argument several times, the matched arguments will be
collected into a list::

    Usage: my_program.py <file> <file> --path=<path>...

I.e. invoked with ``my_program.py file1 file2 --path=./here
--path=./there`` the returned dict will contain ``args['<file>'] ==
['file1', 'file2']`` and ``args['--path'] == ['./here', './there']``.


Option descriptions format
----------------------------------------------------------------------

**Option descriptions** consist of a list of options that you put
below your usage patterns.

It is necessary to list option descriptions in order to specify:

- synonymous short and long options,
- if an option has an argument,
- if option's argument has a default value.

The rules are as follows:

- Every line in ``doc`` that starts with ``-`` or ``--`` (not counting
  spaces) is treated as an option description, e.g.::

    Options:
      --verbose   # GOOD
      -o FILE     # GOOD
    Other: --bad  # BAD, line does not start with dash "-"

- To specify that option has an argument, put a word describing that
  argument after space (or equals "``=``" sign) as shown below. Follow
  either <angular-brackets> or UPPER-CASE convention for options'
  arguments.  You can use comma if you want to separate options. In
  the example below, both lines are valid, however you are recommended
  to stick to a single style.::

    -o FILE --output=FILE       # without comma, with "=" sign
    -i <file>, --input <file>   # with comma, wihtout "=" sing

- Use two spaces to separate options with their informal description::

    --verbose More text.   # BAD, will be treated as if verbose option had
                           # an argument "More", so use 2 spaces instead
    -q        Quit.        # GOOD
    -o FILE   Output file. # GOOD
    --stdout  Use stdout.  # GOOD, 2 spaces

- If you want to set a default value for an option with an argument,
  put it into the option-description, in form ``[default:
  <my-default-value>]``::

    --coefficient=K  The K coefficient [default: 2.95]
    --output=FILE    Output file [default: test.txt]
    --directory=DIR  Some directory [default: ./]

- If the option is not repeatable, the value inside ``[default: ...]``
  will be interpeted as string.  If it *is* repeatable, it will be
  splited into a list on whitespace::

    Usage: my_program.py [--repeatable=<arg> --repeatable=<arg>]
                         [--another-repeatable=<arg>]...
                         [--not-repeatable=<arg>]

    # will be ['./here', './there']
    --repeatable=<arg>          [default: ./here ./there]

    # will be ['./here']
    --another-repeatable=<arg>  [default: ./here]

    # will be './here ./there', because it is not repeatable
    --not-repeatable=<arg>      [default: ./here ./there]

Examples
----------------------------------------------------------------------

We have an extensive list of `examples
<https://github.com/docopt/docopt/tree/master/examples>`_ which cover
every aspect of functionality of **docopt**.  Try them out, read the
source if in doubt.

Subparsers, multi-level help and *huge* applications (like git)
----------------------------------------------------------------------

If you want to split your usage-pattern into several, implement
multi-level help (whith separate help-screen for each subcommand),
want to interface with existing scripts that don't use **docopt**, or
you're building the next "git", you will need the new ``options_first``
parameter (described in API section above). To get you started quickly
we implemented a subset of git command-line interface as an example:
`examples/git
<https://github.com/docopt/docopt/tree/master/examples/git>`_


Data validation
----------------------------------------------------------------------

**docopt** does one thing and does it well: it implements your
command-line interface.  However it does not validate the input data.
On the other hand there are libraries like `python schema
<https://github.com/halst/schema>`_ which make validating data a
breeze.  Take a look at `validation_example.py
<https://github.com/docopt/docopt/tree/master/examples/validation_example.py>`_
which uses **schema** to validate data and report an error to the
user.

Development
======================================================================

We would *love* to hear what you think about **docopt** on our `issues
page <http://github.com/docopt/docopt/issues>`_

Make pull requrests, report bugs, suggest ideas and discuss
**docopt**. You can also drop a line directly to
<vladimir@keleshev.com>.

Porting ``docopt`` to other languages
======================================================================

We think **docopt** is so good, we want to share it beyond the Python
community!

The follosing ports are available:

- `Ruby port <http://github.com/docopt/docopt.rb>`_
- `CoffeeScript port <http://github.com/docopt/docopt.coffee>`_
- `Lua port <http://github.com/docopt/docopt.lua>`_
- `PHP port <http://github.com/docopt/docopt.php>`_

But you can always create a port for your favorite language!  You are
encouraged to use the Python version as a reference implementation.  A
Language-agnostic test suite is bundled with `Python implementation
<http://github.com/docopt/docopt>`_.

Porting discussion is on `issues page
<http://github.com/docopt/docopt/issues>`_.

Changelog
======================================================================

**docopt** follows `semantic versioning <http://semver.org>`_.  The
first release with stable API will be 1.0.0 (soon).  Until then, you
are encouraged to specify explicitly the version in your dependency
tools, e.g.::

    pip install docopt==0.6.2

- 0.6.2 `Wheel <http://pythonwheels.com/>`_ support.
- 0.6.1 Bugfix release.
- 0.6.0 ``options_first`` parameter.
  **Breaking changes**: Corrected ``[options]`` meaning.
  ``argv`` defaults to ``None``.
- 0.5.0 Repeated options/commands are counted or accumulated into a
  list.
- 0.4.2 Bugfix release.
- 0.4.0 Option descriptions become optional,
  support for "``--``" and "``-``" commands.
- 0.3.0 Support for (sub)commands like `git remote add`.
  Introduce ``[options]`` shortcut for any options.
  **Breaking changes**: ``docopt`` returns dictionary.
- 0.2.0 Usage pattern matching. Positional arguments parsing based on
  usage patterns.
  **Breaking changes**: ``docopt`` returns namespace (for arguments),
  not list. Usage pattern is formalized.
- 0.1.0 Initial release. Options-parsing only (based on options
  description).