Restricting values of command line options

Question

How do I restrict the values of the argparse options?

In the below code sau option should only accept a number of 0 or 1 and bg should only allow an integer. How can I implement this?

import os
import sys, getopt
import argparse

def main ():
    parser = argparse.ArgumentParser(description='Test script')
    parser.add_argument('-sau','--set',action='store',dest='set',help='<Required> Set flag',required=True)
    parser.add_argument('-bg','--base_g',action='store',dest='base_g',help='<Required> Base g',required=True)
    results = parser.parse_args() # collect cmd line args
    set = results.set
    base_g = results.base_g

if __name__ == '__main__':
    main()

don't mask the builtin: `set = results.set` (you see the syntax highlighting colour) — eumiro, Dec 28 '12 at 09:51
Also, on a sidenote, if arguments are required, they shouldn't be flags but positional arguments. — Jonas Schäfer, Dec 28 '12 at 09:52

score 71 · Accepted Answer · edited Feb 13 '20 at 14:03

You can use the type= and choices= arguments of add_argument. To accept only '0' and '1', you'd do:

parser.add_argument(…, choices={"0", "1"})

And to accept only integer numbers, you'd do:

parser.add_argument(…, type=int)

Note that in choices, you have to give the options in the type you specified as the type argument. So to check for integers and allow only 0 and 1, you'd do:

parser.add_argument(…, type=int, choices={0, 1})

Example:

>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> _ = parser.add_argument("-p", type=int, choices={0, 1})
>>> parser.parse_args(["-p", "0"])
Namespace(p=0)

Restricting values of command line options

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