Suppressing option processing after a non-option command-line argument

Question

I am writing a wrapper script using argparse which accepts a list of arguments that are going to be passed to another program, and some options that are specific to my wrapper. To avoid confusion regarding which options go where, I want any appearance of a non-option argument to suppress processing further arguments as options, as if a -- argument appeared just before it. In other words, something similar to what xterm -e does.

parse_known_args is obviously wrong, because it will ignore unknown options, and pick up options appearing after a non-option.

What is the best way to accomplish this in Python? I would prefer to keep using argparse over parsing the command line manually.

Asked By: user3840170

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Answer 1

Use nargs=argparse.REMAINDER or nargs=argparse.PARSER. The latter differs in that it makes the remaining arguments required.

Neither is particularly well documented as of April 2023: REMAINDER is barely mentioned twice in the manual (with no explanation what it does), while PARSER is not present in the manual at all, so it looks even more like an implementation detail; perhaps it is not so wise to actually use it. Beware.

>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('argv', nargs=argparse.REMAINDER)
>>> parser.add_argument('--foo', action='store_const', const=True)
>>> print(parser.parse_args(['--foo', 'a', '--foo', 'b']))
Namespace(argv=['a', '--foo', 'b'], foo=True)
>>> print(parser.parse_args(['--foo']))
Namespace(argv=[], foo=True)

>>> import argparse
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('argv', nargs=argparse.PARSER)
>>> parser.add_argument('--foo', action='store_const', const=True)
>>> print(parser.parse_args(['--foo', 'a', '--foo', 'b']))
Namespace(argv=['a', '--foo', 'b'], foo=True)
>>> print(parser.parse_args(['--foo']))
usage: [-h] [--foo] argv ...
: error: the following arguments are required: argv

Answered By: user3840170

Suppressing option processing after a non-option command-line argument

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