It's surprising that -c looks like python -c option, but different. Would you mind to add a help message to explain that there are pdb commands? And that they have the same format than .pdbrc configuration files?

I suggest to add dest='commands', since it's non-obvious from command name that's a list.

I suggest using names longer than 1 letter, you should update the code below as well.

IMO nargs='?' is wrong. You cannot pass no pyfile.

This is a slight work-around for limitations in argparse -- we want the mutually exclusive group behaviour, so nargs='?' is needed.

Which limitation? Is there is a reason to use the wrong nargs on purpose, please add a comment to explain why.

Which limitation? Is there is a reason to use the wrong nargs on purpose, please add a comment to explain why.

I don't think this is wrong. Consider it as - you can either pass a module with -m OR a pyfile. So pyfile is optional, you can pass no pyfile.

That's not how exclusive group works. Either you pass a module or a pyfile. pyfile is not optional.

That's not how exclusive group works. Either you pass a module or a pyfile. pyfile is not optional.

I think either pass a module or a pyfile -> pyfile is optional, it's literally in a either/or sentence.

Mutually exclusive group requires all the options in the group to be "optional". What's your proposal for this? You can't use nargs=1 because that would make pyfile a required argument - and it's not. It's absolutely fine if you don't pass a pyfile when you pass a module (actually you can't pass a pyfile when you pass a module).

Sorry, I misunderstood how exclusive groups work. It's kind of surprising. Apparently, you must use nargs='?'. It's just counter intuitive to me.

import argparse
parser = argparse.ArgumentParser(prog='PROG')
group = parser.add_argument_group()
exclusive_group = group.add_mutually_exclusive_group(required=True)
exclusive_group.add_argument('-m', metavar='MODULE')
exclusive_group.add_argument('pyscript', nargs='?')
print(parser.parse_args(['-m', 'mymod']))
print(parser.parse_args(['myscript']))
print(parser.parse_args([]))

Output:

$ python3 x.py 
Namespace(m='mymod', pyscript=None)
Namespace(m=None, pyscript='myscript')
usage: PROG [-h] (-m MODULE | pyscript)
PROG: error: one of the arguments -m pyscript is required

It's just counter intuitive to me.

This bit of argparse's design is odd, I agree.

A

I would prefer:

if opts.module:
    args = [opts.module]
    ...
else:
    args = [opts.pyfile]
    ...

args.extend(opts.ags)

...

sys.argv = args  # Hide "pdb.py" and pdb options from argument list

This would be a larger refactor, the current state reflects what's currently present.

Right, that's why I'm asking for :-)

The logic is pretty similar right? Just a slightly different implementation. I don't think this is too much if this is preferred.

I'm just disturbed by calling "module" a "file".

Also, feel free to ignore my comment about this code.