I need to list the user-agent. I have to enter %prog --agents WITHOUT ARGUMENTS! But I still write that we need arguments. 
Closed due to the fact that off-topic participants Aleksey Shimansky , αλεχολυτ , ߊߚߤߘ , Denis Bubnov , Sasha Omelchenko Apr 27 '17 at 14:51 .
It seems that this question does not correspond to the subject of the site. Those who voted to close it indicated the following reason:
- “Questions asking for help with debugging (“ why does this code not work? ”) Should include the desired behavior, a specific problem or error, and a minimum code for playing it right in the question . Questions without an explicit description of the problem are useless for other visitors. See How to create minimal, self-sufficient and reproducible example . " - Alexey Shimansky, αλεχολυτ, Denis Bubnov, Sasha Omelchenko
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argparseis not used in it. Related question: argparse module - jfs