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() 

Answer 1

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)