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command line parsing speedster

Project description

Opster is a command line options parser, intended to make writing command line applications easy and painless. It uses built-in Python types (lists, dictionaries, etc) to define options, which makes configuration clear and concise. Additionally it contains possibility to handle subcommands (i.e. hg commit or svn update).


Requires at least Python 2.6

Quick example

That’s an example of an option definition:

import sys
from opster import command

def main(message,
         no_newline=('n', False, "don't print a newline")):
    '''Simple echo program'''
    if not no_newline:

if __name__ == '__main__':

Running this program will print help message:

> ./ invalid arguments [OPTIONS] MESSAGE

Simple echo program


 -n --no-newline  don't print a newline
 -h --help        show help

As you can see, here we have defined option to not print newline: keyword argument name is a long name for option, default value is a 3-tuple, containing short name for an option (can be empty), default value (on base of which processing is applied - see description) and a help string.

Underscores in long names of options are converted into dashes.

If you are calling a command with option using long name, you can supply it partially. In this case it could look like ./ --no-new. This is also true for subcommands: read about them and everything else you’d like to know in documentation.


3.6 (2012.04.23)

  • Now commands can have -h option (GH-2).
  • Better Windows compatibility (GH-18, GH-20).
  • Refactored internal options representation with easier introspectability (GH-19).
  • Tests support Python 3 (GH-21).

Thanks for this release are going to Oscar Benjamin, every point in this release is his work.

3.5 (2012.03.25)

  • Added command.Error to facilitate easy exits from scripts (GH-12).
  • Fixed opster.t output.

3.4 (2012.01.24)

  • Fix for installation issue ( wasn’t included).
  • Fix for complaints (most of them).
  • Fix for script name when calling as a command (and not a dispatcher) (GH-4).
  • Fix for some 2to3 issues (GH-5).
  • Fixed bug with empty arguments for opster.command (GH-6).
  • opster.t is now able to run under dash.
  • More output encodings supported (GH-7).
  • Coverage support for cram tests (GH-8).
  • Fixed combination of varargs and option name with underscore (GH-10).

3.3 (2011.09.04)

  • Multicommands: ability to specify global options before specifying name of command

3.2 (2011.08.27)

  • Fix for TypeError: func() got multiple values for 'argument'

3.1 (2011.08.27)

  • Better aliases support.
  • Fixes for options and usage discovery.
  • Fix for error handling of dictionary options in multicommands.
  • Fix for help not working when global options are defined.

3.0 (2011.08.14)

  • Backward incompatible Single commands now don’t attempt to parse. arguments if you call them. Use function.command() attribute (much like earlier to parse arguments now.
  • Switch to Python 2.6.
  • Ability to have few subcommand dispatchers in a single runtime (no single global CMDTABLE dictionary anymore).

2.2 (2011.03.23)

  • adjust indentation level in multiline docstrings (compare 1 and 2)
  • small fix for internal getopt exception handling

2.1 (2011.01.23)

  • fix help display in case middleware returns original function

2.0 (2011.01.23)

  • fix help display when there is no __doc__ declared for function
  • dict type handling
  • .help() attribute for every function, printing help on call

1.2 (2010.12.29)

  • fix option display for a list of subcommands if docstring starts with a blank line

1.1 (2010.12.07)

  • _completion was failing to work when global options were supplied to command dispatcher

1.0 (2010.12.06)

  • when middleware was used and command called without arguments, instead of help, traceback was displayed

0.9.13 (2010.11.18)

  • fixed exception handling (cleanup previous fix, actually)
  • display only name of application, without full path

0.9.12 (2010.11.02)

  • fixed trouble with non-ascii characters in docstrings

0.9.11 (2010.09.19)

  • fixed exceptions handling
  • autocompletion improvements (skips middleware, ability of options completion)

0.9.10 (2010.04.10)

  • if default value of an option is a fuction, always call it (None is passed in case when option is not supplied)
  • always call a function if it’s default argument for an option
  • some cleanup with better support for python 3
  • initial support for autocompletion (borrowed from PIP)

0.9 - 0.9.9 (since 2009.07.13)

Ancient history ;-)

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