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Re: mypy question

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From: Karsten.Hilbert@gmx.net (Karsten Hilbert)
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Subject: Re: mypy question
Date: Fri, 29 Dec 2023 21:33:36 +0100
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by: Karsten Hilbert - Fri, 29 Dec 2023 20:33 UTC

Am Fri, Dec 29, 2023 at 11:04:59AM -0700 schrieb Mats Wichmann via Python-list:

> >For what it's worth here's the signature of that function:
> >
> > def run_rw_queries (
> > link_obj:_TLnkObj=None,
> > queries:list[dict[str, str | list | dict[str, Any]]]=None,
> > end_tx:bool=False,
> > return_data:bool=None,
> > get_col_idx:bool=False,
> > verbose:bool=False
> > ) -> tuple[list[dbapi.extras.DictRow], dict[str, int] | None]:
> >
> >Given that I would have thought that passing in
> >list[dict[str, str]] for "queries" ought to be type safe.
> >Mypy indicates otherwise which I am not grokking as to why.
>
> ah... didn't grok what you were asking, sorry - ignore my attempt then.

Never mind, the attempt to help is appreciated.

> So you are passing something that has been typed more
> narrowly than the function parameter.

That would then sort of skirt on violation of the Liskov
principle, of which I learned while trying to research this
mypy behaviour.

However, I would not think the above to be a narrowing-down
as it just *selects* one of the explicitely "legal" options.

list[dict[str, str | list | dict[str, Any]]]

should AFAICT expand to:

list[dict[str, dict[str, Any]]]

list[dict[str, list]]

list[dict[str, str]]

the last of which should provide coverage of

[{'some key': 'some value'}]

> Can you use a TypeGuard here?

Not from what I understand about them...

Karsten
--
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I bet the human brain is a kludge. -- Marvin Minsky

devel / comp.lang.python / Re: mypy question

devel / comp.lang.python / Re: mypy question