Mmmh, that may work just fine ! Thanks for that idea, ChrisA, i'm looking forward to implement that.
Best wishes, --lucas On 12/07/2021 21:33, Chris Angelico wrote:
On Tue, Jul 13, 2021 at 5:22 AM lucas <lu...@bourneuf.net> wrote:Hello everyone, Let us consider this patch of code: import argparse def parse_cli() -> argparse.Namespace: parser = argparse.ArgumentParser() parser.add_argument('n', type=int) return parser.parse_args() args = parse_cli() print(args.n + ' ') # type error Running CPython on it will raise a TypeError, and running Mypy on it will indicate that no issues were found. I was wondering if there is any way for me to have mypy detecting the args.n type, based on the type keyword of the parser.add_argument function ? It appears that some type annotations were added to tierce party modules, provided by mypy itself. Is there a technical issue preventing such work to be made for argparse (or other CLI ; i didn't find anything for others either)Seems complicated, since it depends on a lot of run-time information. What if you flip the problem on its head? Instead of creating the argparser and letting that govern the types, maybe create a dataclass, and then programmatically build the parser. from dataclasses import dataclass import argparse @dataclass class Args: n: int def parse_cli() -> Args: parser = argparse.ArgumentParser() for field, typ in Args.__dataclass_fields__.items(): if hasattr(typ, "type"): typ = typ.type # Python 3.10 changed things a bit parser.add_argument(field, type=typ) return Args(**vars(parser.parse_args())) args = parse_cli() print(args.n + ' ') Only barely tested it and didn't try MyPy, but that's the basic idea. You'd have to figure out the tidiest way to define all the other attributes of your arguments (help text, etc), but ideally, all the info should be able to be coded in the dataclass. Incidentally, you could choose to make parse_cli into a classmethod of Args. Might be cleaner. ChrisA
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