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Comment by singularity2001 | Hacker News Reader

singularity2001

Sorry for posting this issue here:

python3 type_annotations.py

    def sum_and_stringify(nums: List[int]) -> str:

NameError: name 'List' is not defined

EDIT: Solved: Either just list or List[int] with import:

from typing import List

Thanks for all the help guys! By the way I took the example from the mypy page. A classical case of 'critical line missing from example code' (as perfectioned by Bjarne Stroustrup back when)

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I think you have to import that.

import List??

At least this works: def sum_and_stringify(nums: list) -> str:

The built-in constructor is `list`, not `List`.

Thanks for all the help guys! by the way I took the example from the mypy page

    def sum_and_stringify(nums: list[int]) -> str:

TypeError: 'type' object is not subscriptable

so either just list or List[int] with import, got it.

A classical case of 'critical line missing from example code' (as perfectioned by Bjarne Stroustrup back when)

Yeah, you need to write `from typing import List` to get the generic List class that you can parameterize with an item type. As you pointed out, you can use the builtin lowercase-l list without importing anything, but that doesn't allow you to specify the item type.

No. Try: from typing import List, TYPE_CHECKING

How I found it: quick google search for "mypy validate list"

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