Type Hint for Constants and Class Attributes: typing.Final

Recipes

New in Python 3.8, see PEP 591.

from typing import Final


# constant
MAX_SIZE: Final = 1024
MAX_SIZE: Final[int] = 1024


# class attribute
class Base:
    ATTR: Final[int] = 10

class Sub(Base):
    ATTR = 1  # Error: cannot be changed in subclasses.


class ImmutablePoint:
    x: Final[int]
    y: Final[int]  # Error: final attribute without an initializer

    def __init__(self) -> None:
        self.x = 1  # Good

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References