How to check if an argument from commandline has been set?

Question

I can call my script like this:

python D:\\myscript.py 60

And in the script I can do:

arg = sys.argv[1]
foo(arg)


        

Answer 1

Don't use sys.argv for handling the command-line interface; there's a module to do that: argparse.

You can mark an argument as required by passing required=True to add_argument.

import argparse
parser = argparse.ArgumentParser(description='Process some integers.')
parser.add_argument("foo", ..., required=True)
parser.parse_args()

Answer 2

if len(sys.argv) == 1:
   print('no arguments passed')
   sys.exit()

This will check if any arguments were passed at all. If there are no arguments, it will exit the script, without running the rest of it.

Answer 3

If you're using Python 2.7/3.2, use the argparse module. Otherwise, use the optparse module. The module takes care of parsing the command-line, and you can check whether the number of positional arguments matches what you expect.

Answer 4

I use optparse module for this but I guess because i am using 2.5 you can use argparse as Alex suggested if you are using 2.7 or greater

Answer 5

if(sys.argv[1]): should work fine, if there are no arguments sys.argv[1] will be (should be) null

Answer 6

len(sys.argv) > 1