Python argument parser list of list or tuple of tuples

python argparse
joedborg picture joedborg · Apr 2, 2012 · Viewed 16.1k times · Source

I'm trying to use argument parser to parse a 3D coordinate so I can use 

--cord 1,2,3 2,4,6 3,6,9

and get 

((1,2,3),(2,4,6),(3,6,9))

My attempt is

import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--cord', help="Coordinate", dest="cord", type=tuple, nargs=3)
args = parser.parse_args(["--cord","1,2,3","2,4,6","3,6,9"])

vars(args) 
{'cord': [('1', ',', '2', ',', '3'),
  ('2', ',', '4', ',', '6'),
  ('3', ',', '6', ',', '9')]}

What would the replacement of the comma be?

Answer

georg picture georg · Apr 2, 2012

You can add your own type. This also allows for additional validations, for example:

def coords(s):
    try:
        x, y, z = map(int, s.split(','))
        return x, y, z
    except:
        raise argparse.ArgumentTypeError("Coordinates must be x,y,z")


parser.add_argument('--cord', help="Coordinate", dest="cord", type=coords, nargs=3)

Related questions

Parsing boolean values with argparse

I would like to use argparse to parse boolean command-line arguments written as "--foo True" or "--foo False". For example: my_program --my_boolean_flag False However, the following test code does not do what I would like: import argparse …

Read More
How can I pass a list as a command-line argument with argparse?

I am trying to pass a list as an argument to a command line program. Is there an argparse option to pass a list as option? parser.add_argument('-l', '--list', type=list, action='store', dest='list', help='<…

Read More
Simple argparse example wanted: 1 argument, 3 results

The documentation for the argparse python module, while excellent I'm sure, is too much for my tiny beginner brain to grasp right now. I don't need to do math on the command line or meddle with formatting lines on the …

Read More