Python argparse module usage

Question

I have a program which is called like this:

program.py add|remove|show

The problem here is that depending on the add/remove/show command it takes a variable number of arguments, just like this:

program.py add "a string" "another string"
program.py remove "a string"
program.py show

So, 'add' command would take 2 string arguments, while 'remove' command would take 1 only argument and 'show' command wouldn't take any argument. I know how to make a basic argument parser using the module argparse, but I don't have much experience with it, so I started from this:

import argparse
parser = argparse.ArgumentParser()
parser.add_argument("command", choices=["add", "remove", "show"])

But I don't know how to continue and how to implement this functionality depending on the command. Thanks in advance.

mgilson · Accepted Answer · 2016-12-21 18:44:15Z

2

You're looking for argparse's subparsers...

parser = argparse.ArgumentParser(prog='PROG')
subparsers = parser.add_subparsers(help='sub-command help')

# create the parser for the "add" command
parser_add = subparsers.add_parser('add', help='add help')
# [example] add an argument to a specific subparser
parser_add.add_argument('bar', type=int, help='bar help')

# create the parser for the "remove" command
parser_remove = subparsers.add_parser('remove', help='remove help')

# create the parser for the "show" command
parser_show = subparsers.add_parser('show', help='show help')

This example code is stolen with very little modification from the language reference documentation.

answered Dec 21, 2016 at 18:44

mgilson

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2 Comments

jacosro Over a year ago

How do I check which option has been chosen and get the correspondent variables?

mgilson Over a year ago

@xBlackout -- the documentation I linked gives advice on that too ... Search the page for a sentence that starts with "One particularly effective way of handling sub-commands". The tl;dr; is that you can use set_defaults to attach a function to the namespace based on which subparser was selected. Then you just call that function to execute the actions associated with the selected subparser.

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