string options when using argparse with python

Question

I'm not quite understanding the following behavior of argparse

parser.add_argument("-option1", type=int, nargs='?', const=1, default=1, choices=xrange(1, 20), help="help message of option1")
parser.add_argument("-option2", type=str, nargs=1, help="help message of option2")

in case of option1, args.option1 is an integer, when provided. in case of option2, args.option2 looks like an array of strings. I have to use args.option2[0] if I want to get the actual string passed with option2

hpaulj · Accepted Answer · 2014-07-26 16:35:43Z

1

This is explained directly in the documentation on nargs. Summarizing:

For nargs=N, if N is an integer, you get a list of N values. Even if N is 1.

For nargs='?', you get a single value (which may be the default).

For nargs left off entirely, you get whatever the default is for the action. If the action is, e.g., store, that means a single value, not a list of one value.

It even explicitly points out exactly the part that's surprised you:

Note that nargs=1 produces a list of one item. This is different from the default, in which the item is produced by itself.

edited Jul 26, 2014 at 16:35

hpaulj

233k14 gold badges260 silver badges392 bronze badges

answered Jul 25, 2014 at 22:33

abarnert

368k54 gold badges626 silver badges691 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

string options when using argparse with python

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related