migrate to argparse

[thiell]

Migrate to argparse which is more powerful and would provide an easy way to create tools based on the clustershell library. Will also help for Python 3 support (#239).

Usefulness:

• easily implement tools that have default command line options: -w/-x, -b, ... (#295)
• allow to specify an optional value for a specific argument just using nargs='?' (https://docs.python.org/2/library/argparse.html#nargs), will be useful for --pick

Official argparse doc pages:

• https://docs.python.org/2/library/argparse.html
• https://docs.python.org/3/library/argparse.html

Tutorial:

• https://docs.python.org/2/howto/argparse.html

Example of argparse implementation I like:

• https://github.com/google/oauth2client/blob/master/oauth2client/tools.py

Here argparser created in this tools module actually enables scripts to easily inherit oauth2 options:

from oauth2client import tools

def create_parser():
    parser = argparse.ArgumentParser(add_help=False)
    # add scripts custom options
    #parser.add_argument(...)
    return argparse.ArgumentParser(parents=[tools.argparser, parser])

The idea is to create a argparser per group of command line options. The obvious one is for manipulating node sets (-w/-x etc.).

Note: Before Python 2.7/3.2, python-argparse will become a new dependency, but it is easily available (even available in EPEL5, just saying :)).

[asteven]

Why not go with click instead? Have been using this for a while and it's so much nicer then argparse and friends.

[thiell]

Thanks @asteven for the suggestion. I never used click before. I tried to migrate clustershell's cli to argparse with no functional changes but it's tough.

[asteven]

I'm currently more interested in ClusterShell as a library then the cli tools. But if you happen to like click and decide to go with it I may be able to contribute. Thanks for Python3 support btw. Much appreciated.