opterator 0.4

Easy option parsing introspected from function signature.

Opterator is an option parsing script for Python that takes the boilerplate out of option parsing.

Opterator is based on the idea that a main() function for a script can be decorated to allow command-line arguments to be translated into method parameters. This allows it to be self-documenting, and reduces errors in creating and assigning options. I don’t know if you’d want to use it for large scripts, but it’s really useful for quick and dirty ones where you can’t decide if you want to bother with optparse, but querying sys.argv manually is a bit too complicated.

For example, an optparse program for renaming a file might look like this:

from optparse import OptionParser
def main():
    '''main entrypoint for renaming files. Accept two options, backup
    and interactive'''
    parser = OptionParser(usage="A script for renaming files")
    parser.add_option('-b', '--backup', action=store_true,
        help='backup the file')
    parser.add_option('-p', '--interactive', action=store_true,
        help='interactively move files')
    # Move the file

if __name__ == '__main__':
    main()

The equivalent code using opterator looks like this:

from opterator import opterate
@opterate
def main(source, dest, backup=False, interactive=False):
    '''A script for renaming files
    :param backup: backup the file
    :param interactive: -p --interactive interatively
    move files...     '''
    # Move the file

if __name__ == '__main__':
    main()

Opterator automatically generates help messages from the docstring. The main part of the docstring becomes the main part of the help string. The individual parameter docstrings become the helptext for the arguments. By default, the long and short form of a given parameter come from the parameter name and the first character of the parameter name. You can replace either or both of these by adding options that begin with a - character between the parameter and the helptext.

If your main function looks like this:

@opterate
def main(filename1, filename2, recursive=False, backup=False,
        suffix='~', *other_filenames):
    '''An example copy script with some example parameters that might
    be used in a copy command.

    :param recursive: copy directories
        recursively
    :param backup: -b --backup backup any files you copy over
    :param suffix: -S --suffix override the usual backup
        suffix '''
    pass

Your help text will look like this:

dusty:opterator $ python copy.py -h
Usage: copy.py [options] filename1 filename2 [other_filenames]

An example copy script with some example parameters that might
    be used in a copy command.

Options:
  -h, --help            show this help message and exit
  -r, --recursive       copy directories recursively
  -b, --backup          backup any files you copy over
  -S SUFFIX, --suffix=SUFFIX
                        override the usual backup suffix