CODEWITHSUNDEEP
pythoncommand-line-arguments
ying17zi
ying17zi

Reputation: 502

In Python, is there a better way to deal with command line options when each option could have several arguments

I've a Python app like this:

$ app.py -a arg1 -a arg2 -b file1.b -b file2.b

Depending on the option, in app.py, I use two different functions to process the input files. As each option can have several file arguments, I would like something like this:

$ app.py -a arg1 arg2 -b *.b

After searching on the net, I find these three modules: getopt, argparse, optparse

And I wrote a simple one for my app:

optionDict= {'-a':aFunction, '-b':bFunction}
for arg in sys.argv[1:]:
    if arg in optionDict: # arg is an option here.
        funcName = optionDict[arg]
    else: # arg is not an option, then it's a fileName. Deal with this file with the function found according to previous arg.
        funcName(arg)

My quesion: Are there any other modules or better ways to do this?

Upvotes: 1

Views: 335

Answers (3)

ndemou
ndemou

Reputation: 5536

Since 2012 Python has an easy, powerful and very cool module for argument parsing called docopt. It works with Python from 2.5 to 3.3 and needs no installation. Here is the code for your particular case:

'''app.py

Usage:
  app.py -a ARG ... -b FILE ...
  app.py (-h | -v) 

'''
from docopt import docopt
args = docopt(__doc__, version='1.0')
# now do something based on the value of args dict

So this is it: one line of code plus your doc string which is essential. I told you it's cool -- didn't I ;-)

Upvotes: 2

Hernan
Hernan

Reputation: 6063

I think that argparse is the way to go. It does a great job, it is easy to use and in the standard library since 2.7. Take a look a the nargs argument. From the docs

Fixed elements to consume

parser = argparse.ArgumentParser() parser.add_argument('--foo', nargs=2) parser.add_argument('bar', nargs=1) parser.parse_args('c --foo a b'.split()) Namespace(bar=['c'], foo=['a', 'b'])

One arg will be consumed from the command line if possible, and produced as a single item. If no command-line arg is present, the value from default will be produced

parser = argparse.ArgumentParser() parser.add_argument('--foo', nargs='?', const='c', default='d') parser.add_argument('bar', nargs='?', default='d') parser.parse_args('XX --foo YY'.split()) Namespace(bar='XX', foo='YY') parser.parse_args('XX --foo'.split()) Namespace(bar='XX', foo='c') parser.parse_args(''.split()) Namespace(bar='d', foo='d')

All command-line args present are gathered into a list.

parser = argparse.ArgumentParser() parser.add_argument('--foo', nargs='*') parser.add_argument('--bar', nargs='*') parser.add_argument('baz', nargs='*') parser.parse_args('a b --foo x y --bar 1 2'.split()) Namespace(bar=['1', '2'], baz=['a', 'b'], foo=['x', 'y'])

Upvotes: 1

Michael Dillon
Michael Dillon

Reputation: 32392

If you found argparse to be too hard to get started with because of the complexity, then you would probably like plac which is available on PyPi. It is a wrapper around argparse which hides the complexity, and it takes care of a lot of boilerplate argument checking for you.

It works for both Python 2 and 3, and has a decorator that allows Python 2 users to get access to a nice Python 3 feature for function parameters. And you can even nest commands in one another so that you could have -arguments (beginning with dash) and .arguments (beginning with dot) on one command line.

Here are the docs http://plac.googlecode.com/hg/doc/plac.html

Upvotes: 1

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