How can I do really cheap command line parsing in Python?

Question

I've been making heavy use of the answer in "Really Cheap Command-Line Option Parsing in Ruby". It's great and for my purposes, always what I need.

Now I find myself back in Python land for a bit because of internal library support for something I want to do. I'm considering porting it to Ruby but that's beyond the scope of this question, but I'd like to use something similar.

Here is the really cheap method I use often in Ruby:

$quiet       = ARGV.delete('-d')
$interactive = ARGV.delete('-i')

If there is a "-d" in the ARGV array, then $quiet is set to "-d" and not nil. If there is no "-d", then $quiet becomes nil.

Is there something similar I could do in Python?

I am familiar with argparse but it's more heavy weight than what I posted above IIRC. — Ramy, Jul 19 '13 at 20:26

score 6 · Accepted Answer · edited Jul 20 '13 at 04:14

6

You might want to use sys.argv:

from sys import argv
quiet = '-d' in argv # True if '-d' in argv else False

If you want to remove '-d' from the argv, change the second line to this:

quiet = '-d' in argv and (argv.remove('-d') or True)

If this reduces its cheapness, let's make a function of it:

getArg = lambda x: x in argv and (argv.remove(x) or True)
quiet = getArg('-d')
interactive = getArg('-i')

edited Jul 20 '13 at 04:14

the Tin Man

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answered Jul 19 '13 at 20:23

rnbguy

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Really Cheap, fits requirements – Stephan Jul 19 '13 at 20:33
Absolutely. Does what's wanted. – Jiminion Jul 19 '13 at 21:15
1

Doesn't remove the option from the args if it's found, which makes using what's left over (as filenames etc.) harder. – kindall Jul 19 '13 at 21:29
@kindall change the line as this : `quiet = '-d' in argv and (argv.remove('-d') or True)` – rnbguy Jul 19 '13 at 21:44
better to write a small one liner function then. :) – rnbguy Jul 19 '13 at 21:47
once you're writing the one line function though, i think you've already lost the cheapness. Luckily I don't *need* to remove the arguments from the array - that's just the functionality provided in Ruby. – Ramy Jul 22 '13 at 19:34

score 2 · Answer 2 · answered Jul 19 '13 at 20:24

2

Python has a few nice libraries for argument parsing:

Example:

import argparse

parser = argparse.ArgumentParser()
parser.add_argument("-d", action='store_true')

answered Jul 19 '13 at 20:24

jh314

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score 1 · Answer 3 · answered Jul 19 '13 at 20:23

1

Try this:

import sys

quiet = 1 if "-d" in sys.argv else None

answered Jul 19 '13 at 20:23

JoshG79

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This works accurately but mbcoder's response is a bit more thorough and provides a shorter syntax I was looking for. – Ramy Jul 22 '13 at 19:32

score 1 · Answer 4 · edited Jul 19 '13 at 20:58

1

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("-d", action='store_true')

args = parser.parse_args()

if (args.d):
   Print "D switch is on!"

edited Jul 19 '13 at 20:58

Arup Rakshit

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answered Jul 19 '13 at 20:23

Jiminion

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don't you need to make a new argparser object first? something like `parser = argparse.ArgumentParser(description='Process some integers.')` from http://docs.python.org/dev/library/argparse.html – Ramy Jul 19 '13 at 20:34
Yes. Like jh314 sez. – Jiminion Jul 19 '13 at 20:36

kindall · Answer 5 · 2013-07-19T21:49:52.230

IMHO, the lightest way (if you don't want to use argparse) is going to be a helper function:

import sys

def flag(arg):
    try:
        index = sys.argv.index(arg)
    except ValueError:
        return None
    else:
        return sys.argv.pop(index)

Usage:

quiet, interactive = flag("-d"), flag("-i")

Of course, since these are just flags, you could return True and False instead of None and the arg, but I've tried to keep it as similar to the Ruby functionality as posisble.

How can I do really cheap command line parsing in Python?

5 Answers5