https://docs.python.org/3/library/argparse.html#choices says "These can be handled by passing a container object as the choices keyword argument to add_argument()".

I think this should be "iterable" instead. Internally, argparse reads the iterable and converts it to a list so that it can read it multiple times (among other reasons, I'm sure). One of the examples uses range(), which is not a container.

"container" is also used in https://docs.python.org/3/library/argparse.html#the-add-argument-method

Bonus points for fixing the docstring in argparse.py. I didn't check if anywhere else in that file needs to be fixed.

Can I work on this?

shireenrao: yes, please! As they say, PR's accepted!

I'll warn you that I think the only way this could become newcomer-unfriendly is if there are objections that "iterable" is too much jargon for the argparse documentation. But I'll argue that there's a separate tutorial for beginners, and that the documentation should be precise.

Done. Thank you.

Actually, I might have mislead you on this. I now think that plain iterators won't work. I'm still researching this, I'll get back to you on it. I apologize if it turns out I wasted your time.

Not at all. I just started contributing to cpython 2 days ago and finally got the hang of it and was able to push this without any issues on my side. So either way I would still call this a win for me :)

Sorry, shireenrao, but I'm closing this. It's entirely my error: I misread the source where it was converting this to a list.

The requirement is really that it be something you can iterate over multiple times, and supports "in". I guess "container object" is as good as anything for that.

Again, sorry to waste your time, but I'm glad you got something out of the experience. If you're working on another issue and need some help or a review, please let me know.

Can you close your PR, or do you want me to?

I understand eric.smith. I can close this PR. 

I currently have the following 3 other PR's waiting for review on github -
https://github.com/python/cpython/pull/15180
https://github.com/python/cpython/pull/15170
https://github.com/python/cpython/pull/15149

Would appreciate it if you could take a look :)