Library / toolkit for creating command line programs with minimal effort.

Pycommand is essentially a fancy wrapper around getopt that consists of one simple CommandBase class that you can inherit to create executable commands for your (Python) programs with very simplistic and readable code. It has support for subcommands and also nesting commands, so you can create (multiple levels of) subcommands, with the ability to pass the values of optional arguments of a command object to its subcommand objects. Supported Python versions are 2.7 and 3.2 and later.

• Documentation: https://babab.github.io/pycommand/
• PyPI: https://pypi.python.org/pypi/pycommand/
• Github: https://github.com/babab/pycommand

• Parsing of optional and positional arguments
• Minimalistic approach with a clean API
• Create scripts in a matter of minutes using the code generator
• Auto compiled usage messages
• Graceful semi-automatic handling of exit status codes
• Subcommands can have subcommands that can have subcommands (each with their own optional arguments)
• Pass values for --some-option from a parent command into child commands.

If you have pip installed, you can just do:

# pip install pycommand

To quickly start writing a command from a template (much like the examples below), use the script generator by running:

$ python -m pycommand init

This will ask you for an executable name, class name and template type and it will save it to an executable python script, ready to be used as a command line program.

You can have a very basic command line program that handles -v, --version and -h, --help arguments set up in less than a minute.

For full documentation and examples, visit http://pythonhosted.org/pycommand/

Here is an undocumented code example of getting automated usage text generation and parsing of optional arguments. If we name the script for which you can see the code below basic-example and execute it, the following will be the output for running basic-example -h or basic-example --help:

usage: basic-example [options]

An example of a basic CLI program

Options:
-h, --help                        show this help information
-f <filename>, --file=<filename>  use specified file
--version                         show version information

And here is the code:

#!/usr/bin/env python

import pycommand
import sys


class BasicExampleCommand(pycommand.CommandBase):
    '''An example of a basic CLI program'''
    usagestr = 'usage: basic-example [options]'
    description = __doc__

    optionList = (
        ('help', ('h', False, 'show this help information')),
        ('file', ('f', '<filename>', 'use specified file')),
        ('version', ('', False, 'show version information')),
    )

    def run(self):
        if self.flags.help:
            print(self.usage)
            return 0
        elif self.flags.version:
            print('Python version ' + sys.version.split()[0])
            return 0
        elif self.flags.file:
            print('filename = ' + self.flags.file)
            return 0

        print('Program completed. Try adding "--help"')

if __name__ == '__main__':
    # Shortcut for reading from sys.argv[1:] and sys.exit(status)
    pycommand.run_and_exit(BasicExampleCommand)

    # The shortcut is equivalent to the following:

    # cmd = BasicExampleCommand(sys.argv[1:])
    # if cmd.error:
    #     print('error: {0}'.format(cmd.error))
    #     sys.exit(1)
    # else:
    #     sys.exit(cmd.run())

When parsing command line program arguments, I sometimes work with argparse (a replacement for optparse). I don't really like the API and the output it gives, which is the main reason I've always used getopt for parsing arguments whenever possible.

The CommandBase class was originally written for DisPass, which is a password manager/generator, as a means to easily define new subcommands and have auto-generated usage messages. Because I want to have this in other projects I've decided to put it in the cheeseshop in 2013. It has since been refined for more generic usage and has proven to be stable and workable throughout the years.

Copyright (c) 2013-2016, 2018 Benjamin Althues <benjamin@babab.nl>

Permission to use, copy, modify, and distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.