How to parse one group out of the two groups of command line arguments using argparse in Python3?

Question

I want to develop a CLI that takes one of the two pairs of arguments together:

group-resources --limit 5

or

group-overlap --groups group1,group2

The group-resources is positional and limit is required. Same rules are for the rest of the two. However, my current code makes it a compulsion that all four are required.

My current code:

import argparse

import analysis
import cleanup
import etl
import initialize_db

parser = argparse.ArgumentParser(
    description='Inventory DB for Cloud Infrastructure')
parser.add_argument(
    'group-resources', help='List top k groups as per their memory, disk, and cpu count.')
parser.add_argument(
    '--limit', help='Number of groups in descending order of their resources.', type=int, required=True)
parser.add_argument(
    'group-overlap', help='Fetch nodes that belong in both the groups')
parser.add_argument(
    '--groups', help='specify the group names separated by a comma.', type=str, required=True
)

args = parser.parse_args()

print(args)

When I run python3 cli.py group-resources --limit 5 , I get the following error:

usage: cli.py [-h] --limit LIMIT --groups GROUPS group-resources group-overlap
cli.py: error: the following arguments are required: group-overlap, --groups

I want that if I provide group-resources and limit, or if I provide group-overlap and groups, then my code should work. No other permutation should be allowed. How do I do that?

Answer 1

We can use subparsers . Here is how we can do with slight modification in your code.

import argparse

parser = argparse.ArgumentParser(
    description='Inventory DB for Cloud Infrastructure')

subparsers = parser.add_subparsers(help='types of arguments')

group_resources_parser = subparsers.add_parser("group-resources", help='List top k groups as per their memory, disk, and cpu count.')
group_overlap_parser = subparsers.add_parser("group-overlap", help='Fetch nodes that belong in both the groups')
group_resources_parser.add_argument(
    '--limit', help='Number of groups in descending order of their resources.', type=int, required=True)
group_overlap_parser.add_argument(
    '--groups', help='specify the group names separated by a comma.', type=str, required=True
)

args = parser.parse_args()

print(args)

Examples:

1. python3 cli.py group-resources

    usage: cli.py group-resources [-h] --limit LIMIT cli.py group-resources: error: the following arguments are required: --limit

2. python3 cli.py group-overlap

    usage: cli.py group-overlap [-h] --groups GROUPS cli.py group-overlap: error: the following arguments are required: --groups

3. python3 cli.py group-resources --limit 5 group-overlap

    usage: cli.py [-h] {group-resources,group-overlap} ... cli.py: error: unrecognized arguments: group-overlap