python - Example code from typing library causes TypeError: 'type' object is not subscriptable, why?

Question

Considering to Python Docs for typing why code below isn't working?

>>> Vector = list[float]
Traceback (most recent call last):
  File "<input>", line 1, in <module>
TypeError: 'type' object is not subscriptable

In docs there is the same example as I mentioned above. here

Vector = list[float]

def scale(scalar: float, vector: Vector) -> Vector:
    return [scalar * num for num in vector]

I didn't find question about this example.

Answer 1

The ability to use the [] operator on types like list for type hinting was added in 3.9.

https://docs.python.org/3/whatsnew/3.9.html#type-hinting-generics-in-standard-collections

In earlier versions it will generate the error you describe, and you need to import List object from typing instead.

from typing import List
List[float]