When using nargs='*' with other required arguments, argparse incorrectly says the optional argument is required.

Output (with no arguments)

usage: example [-h] foo [bar ...]
example: error: the following arguments are required: foo, bar

Code

import argparse

parser = argparse.ArgumentParser(prog='example')
parser.add_argument('foo')
parser.add_argument('bar', nargs='*')
args = parser.parse_args()

Python 3.9.16

Linked PRs

• GH-103219: Fix optional args incorrectly being processed as required args #123931