Most pythonic way of accepting arguments using optparse

Question

I currently have a python file that utilizes sys.argv[1] to accept a string at the command line. It then performs operations on that string and then returns the modified string to the command line.

I would like to implement a batch mode option in which I can provide a file of strings (one per line, fwiw) and have it return to the command line so that I can redirect the output doing something like

$ python script.py -someflag file.txt > modified.txt 

while still retaining the current capabilities.

I am only running 2.6, so argparse is not an option. The tutorials I have seen either use argparse, getopt, or delve into examples that are too complex/don't apply.

What is the best way to check the input and act appropriately?

Presber

argparse is still an option, it's just not built into 2.6. You can still install it like any 3rd party package (for example, pip install argparse). – Gradygrae

Answer 1

argparse is still an option, it's just not built into 2.6. You can still install it like any 3rd party package (for example, using easy_install argparse).

An example of code for this would be:

import sys
import argparse

p = argparse.ArgumentParser(description="script.py")
p.add_argument("-s", dest="string")
p.add_argument("-f", dest="infile")

args = p.parse_args()

if args.infile == None and args.string == None:
    print "Must be given either a string or a file"
    sys.exit(1)
if args.infile != None and args.string != None:
    print "Must be given either a string or a file, not both"
    sys.exit(1)
if args.infile:
    # process the input file one string at a time
if args.string:
    # process the single string

Gradygrae

Thank you! I didn't know that argparse was third-party before 2.7, and the code is an added bonus. I will likely accept this as soon as I get a chance to try it out :) – Presber

You're quite welcome. argparse is a very powerful and intuitive tool and I highly recommend it. – Gradygrae

When testing against None, it is more pythonic to use is and is not to test for that value: if args.infile is None and args.string is None: and if args.infile is not None and args.string is not None:. – Economist

Answer 2

See my answer here: What's the best way to grab/parse command line arguments passed to a Python script?

As a shortcut, here's some sample code:

import optparse

parser = optparse.OptionParser()

parser.add_option('-q', '--query',
    action="store", dest="query",
    help="query string", default="spam")

options, args = parser.parse_args()

print 'Query string:', options.query

Erepsin

Note: Using optparse is discouraged since python version 2.7. The optparse module is deprecated and will not be developed further; development will continue with the argparse module. See PEP 0389 for more info. – Chlorothiazide