Passing Python variables via command line?

Question

I'm new to Python (as in, yesterday), so bear with me if I don't know 'the obvious' yet.

There are two ways I could go about this, and either would work fine for me, and I'm not sure if getopt or optparse contains what I want/need (from what I'm reading)? I would like to do something similar to the following:

python this.py --variable VariableName="Value" -v VariableName2="Value2"

OR

python this.py --VariableName "Value"

The main issue I'm facing is that I may need to optionally pass any of the variables in, but not necessarily all and in any particular order (ergo, a raw sys.argv won't work in my case). For some of these variables, I may be passing strings, numbers and/or arrays.

Once the variables are passed in the script, one way or another I'll need to check if they are set / not null and assign default values as necessary.

Thanks!

Answer 1

You definitely want a commandline argument parser. Python ships with a few. Python2.7 has argparse which can be back-ported to earlier versions as necessary and is what I would recommend. There's also optparse . It's not quite as nice as argparse , but it can still do a good bit and is available with older python versions as well as newer ones.

There's also getopt , but that one is hardly worth mentioning in comparison to the others.

Answer 2

I'm going to do a first and answer my own question.

As much as I like the answer @mgilson gave, I found an 'easier' way. I'm very comfortable with regular expressions, and figuring out an associative array (ie, Dictionary) isn't too difficult.

import re

args = {}
args['pythonFile'] =  sys.argv[0]

for arg in sys.argv[1:]:
  variable = re.search('\-\-(.*)\=',arg)
  variable = variable.group(1)
  value = re.search('\=(.*)',arg)
  value = value.group(1)
  args[variable] = value

print args

Here's the proof:

$ /opt/python27/bin/python2.7 Test.py --var1=1 --var2="Testing This"
{'var1': '1', 'pythonFile': 'Test.py', 'var2': 'Testing This'}

Woot!

Answer 3

I refactored the above code a little to be more flexible and modular (great solution by the way). You can now add something like --dev instead of --dev=true . Or you can do both. It also wont crash the app if you don't add any args.

def get_cli_args():
    """
    Returns a dictionary of arguments passed to through the CLI.
    """

    import re
    import sys

    args = {}

    for arg in sys.argv[1:]:
        var = re.search('\-\-([A-Za-z]*)', arg) # optional value assignment
        var = var.group(1)
        value = re.search('\=(.*)', arg)
        value = value.group(1) if value else None
        args[var] = value

    return args