Type annotation for dict.items()

user_18046894 0
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Sample code:

def test() -> list[tuple[str, int]]:
    some_dict = {"some": 3, "another": 5}
    return some_dict.items()

For me it's quite obvious that it returns list of tuples: [("some", 3), ("another": 5)].

But dict.items() actually returns dict_items[("some", 3), ("another", 5)] and above result can be only achieved when casting it to list.

I wanted to have type annotation for this case, but list[tuple[str, int]] isn't working (checked with MyPy version 0.961) and I can't find anywhere how to annotate dict_items.

How to annotate function like this (without casting it to list, and preserving information about return type, not just Any)?

python-3.10 python-typing mypy python
1 Answers

Use ItemsView:

from typing import ItemsView


def test() -> ItemsView[str, int]:
    some_dict = {"some": 3, "another": 5}
    return some_dict.items()

Output (mypy)

Success: no issues found in 1 source file

In Python 3.9+ use instead:

from collections.abc import ItemsView

A more "general" solution would be to use Iterable:

from collections.abc import Iterable

def test() -> Iterable[tuple[str, int]]:
    some_dict = {"some": 3, "another": 5}
    return some_dict.items()

but on a personal note I prefer to stick with Postel's Law:

"be conservative in what you send, be liberal in what you accept"

user_40015920
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