pycommand 0.4.0 ****************************************************************************** .. toctree:: :maxdepth: 2 **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 Features ======== - 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. Download and install ==================== If you have pip installed, you can just do: .. code-block:: console # pip install pycommand Script generator ================ To quickly start writing a command from a template (much like the examples below), use the script generator by running: .. code-block:: console $ 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. Example #1 - A Basic command ============================ Here is a demonstration of the 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``: .. code-block:: console usage: basic-example [options] An example of a basic CLI program Options: -h, --help show this help information -f , --file= use specified file --version show version information And here is the code: .. code-block:: python #!/usr/bin/env python import pycommand import sys class BasicExampleCommand(pycommand.CommandBase): '''An example of a basic CLI program This is an example that demonstrates the handling of all possible settings for the optional arguments, managed via the `optionList`. This example does not handle positional arguments. ''' usagestr = 'usage: basic-example [options]' description = __doc__.split('\n')[0] # optionList is a tuple of 2-tuples, in format: # (long-option, (short-option, argument, help-information)) # # The order in which you define the options will be the order # in which they will appear in the usage message optionList = ( ('help', ('h', False, 'show this help information')), # To specify that an option requires an argument just add a # string that describes it ('file', ('f', '', 'use specified file')), # Use an empty string to ommit short option. Long option names # cannot be ommitted, since they are used as dictionary keys in # `self.flags` which holds the validated input ('version', ('', False, 'show version information')), ) def run(self): '''The `run` method of the main command You need to define a method in your class that actually deals with any options that the user of your program has set. We call it `run` here, but you can name it whatever you want. After the object has been created, there are 4 instance variables ready for you to use to write the flow of the program. In this example we only use the following three:: error -- Thrown by GetoptError when parsing illegal arguments flags -- Object/dict of parsed options and corresponding arguments, if any. usage -- String with usage information. The string is compiled using the values found for `usagestr`, `description`, `optionList` and `usageTextExtra`. ''' 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()) Example #2 - Full example of one main command with two subcommands ================================================================== Here is a full example demonstrating essentially the same program, but with the ``--help`` and ``--version`` options replaced for subcommands: .. code-block:: python #!/usr/bin/env python import pycommand import sys class VersionCommand(pycommand.CommandBase): usagestr = 'usage: full-example version' description = 'Show version information' def run(self): print('Python version ' + sys.version.split()[0]) print('Fileflag = {0}'.format(self.parentFlags['file'])) class HelpCommand(pycommand.CommandBase): usagestr = 'usage: full-example help []' description = 'Show help information' def run(self): if self.args and self.args[0] == 'version': print(VersionCommand([]).usage) print(cmd.usage) class FullExampleCommand(pycommand.CommandBase): '''An full example of a pycommand CLI program This is an example that demonstrates the mapping of subcommands and registrering the --file flag from the main command to its subcommand. It only explains new concepts that are not handled in ``basic-example``, so be sure to see that first. ''' usagestr = 'usage: full-example [-f ] []' description = ( 'Commands:\n' ' help show this help information\n' ' version show full version information' ) # Mapping of subcommands commands = {'help': HelpCommand, 'version': VersionCommand} optionList = (('file', ('f', '', 'use specified file')), ) # Optional extra usage information usageTextExtra = ( "See 'full-example help ' for more information on a " "specific command." ) def run(self): '''The `run` method of the main command After the object has been created, there are 4 instance variables ready for you to use to write the flow of the program. In this example we use them all:: error -- Thrown by GetoptError when parsing illegal arguments flags -- OrderedDict of parsed options and corresponding arguments, if any. usage -- String with usage information. The string is compiled using the values found for `usagestr`, `description`, `optionList` and `usageTextExtra`. parentFlags -- Dict of registered `flags` of another `CommandBase` object. ''' try: cmd = super(FullExampleCommand, self).run() except pycommand.CommandExit as e: return e.err # Register a flag of a parent command # :Parameters: # - `optionName`: String. Name of option # - `value`: Mixed. Value of parsed flag` cmd.registerParentFlag('file', self.flags.file) if cmd.error: print('full-example {cmd}: {error}' .format(cmd=self.args[0], error=cmd.error)) return 1 else: return cmd.run() if __name__ == '__main__': # Shortcut for reading from sys.argv[1:] and sys.exit(status) pycommand.run_and_exit(FullExampleCommand) And here are some output examples: .. code-block:: console $ ./full-example usage: full-example [-f ] [] Commands: help show this help information version show full version information Options: -f , --file= use specified file See 'full-example help ' for more information on a specific command. $ ./full-example help version usage: full-example version Show version information $ ./full-example -f error: option -f requires argument $ ./full-example -f somefilename version Python version 3.3.2 Fileflag = somefilename $ ./full-example version Python version 3.3.2 Fileflag = None $ ./full-example help doesnotexist error: command doesnotexist does not exist API documentation ================== .. autoclass:: pycommand.CommandBase :members: .. autofunction:: pycommand.run_and_exit Why was it created? =================== 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. .. include:: ../CHANGELOG.rst Software license ================ Copyright (c) 2013-2016, 2018 Benjamin Althues 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. 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