Using the same option multiple times in Python's argparse

This is simple; just add both action='append' and nargs='*' (or '+').

import argparse parser = argparse.ArgumentParser() parser.add_argument('-i', action='append', nargs='+') args = parser.parse_args() 

Then when you run it, you get

In [32]: run test.py -i input1_url input1_name input1_other_var -i input2_url i ...: nput2_name input2_other_var -i input3_url input3_name In [33]: args.i Out[33]: [['input1_url', 'input1_name', 'input1_other_var'], ['input2_url', 'input2_name', 'input2_other_var'], ['input3_url', 'input3_name']] 

-i should be configured to accept 3 arguments and to use the append action.

>>> p = argparse.ArgumentParser() >>> p.add_argument("-i", nargs=3, action='append') _AppendAction(...) >>> p.parse_args("-i a b c -i d e f -i g h i".split()) Namespace(i=[['a', 'b', 'c'], ['d', 'e', 'f'], ['g', 'h', 'i']]) 

To handle an optional value, you might try using a simple custom type. In this case, the argument to -i is a single comma-delimited string, with the number of splits limited to 2. You would need to post-process the values to ensure there are at least two values specified.

>>> p.add_argument("-i", type=lambda x: x.split(",", 2), action='append') >>> print p.parse_args("-i a,b,c -i d,e -i g,h,i,j".split()) Namespace(i=[['a', 'b', 'c'], ['d', 'e'], ['g', 'h', 'i,j']]) 

For more control, define a custom action. This one extends the built-in _AppendAction (used by action='append'), but just does some range checking on the number of arguments given to -i.

class TwoOrThree(argparse._AppendAction): def __call__(self, parser, namespace, values, option_string=None): if not (2 <= len(values) <= 3): raise argparse.ArgumentError(self, "%s takes 2 or 3 values, %d given" % (option_string, len(values))) super(TwoOrThree, self).__call__(parser, namespace, values, option_string) p.add_argument("-i", nargs='+', action=TwoOrThree) 

If you use action='append' in add_argument() then you will get arguments in list(s) within a list every time you add the option.

As you liked:

[ ["input1_url", "input1_name", "input1_other"], ["input2_url", "input2_name", "input2_other"], ["input3_url", "input3_name"] ] 

But if anyone wants those arguments in the same list[], then use action='extend' instead of action='append' in your code. This will give you those arguments in a single list.

[ "input1_url", "input1_name", "input1_other", "input2_url", "input2_name", "input2_other", "input3_url", "input3_name" ] 

I used combination of nargs=1 and action="append" for optional argument and got what I wanted

#!/usr/bin/env python3 """Argparse test""" from typing import List import argparse import sys import textwrap if __name__ == "__main__": descr = textwrap.dedent( """\ Demonstrate multiple optional attts """ ) usage = textwrap.dedent( """\ test.py [-d] [-s val] file file """ ) parser = argparse.ArgumentParser( prog="test.py", description=descr, usage=usage, formatter_class=argparse.RawTextHelpFormatter, ) parser.add_argument("-d", "--debug", action="store_true", help="set debug output") parser.add_argument("-s", "--skip", nargs = 1, action="append", help="skip") parser.add_argument("files", nargs=2, help="files") args = parser.parse_args() skip_list: List[str] = [] # Note: args.skip is a list of lists if args.skip is not None: for inner_list in args.skip: for val in inner_list: skip_list.append(val) print(f"debug={args.debug}") print(f"skip-list={skip_list}") print(f"files={args.files}") sys.exit() 

It works as expected

>./test.py file_a file_b debug=False skip-list=[] files=['file_a', 'file_b'] ~/python_test > ./test.py -d -s a -s b file_a file_b debug=True skip-list=['a', 'b'] files=['file_a', 'file_b']