`final` keyword equivalent for variables in Python?

Question

I couldn\'t find documentation on an equivalent of Java\'s final in Python, is there such a thing?

I\'m creating a snapshot of an object (used for restorati

Answer 1

Python 3.8 (via PEP 591) adds Final variables, functions, methods and classes. Here are some ways to use it:

@final Decorator (classes, methods)

from typing import final

@final
class Base:
    # Cannot inherit from Base

class Base:
    @final
    def foo(self):
        # Cannot override foo in subclass

Final annotation

from typing import Final

PI: Final[float] = 3.14159     # Cannot set PI to another value
KM_IN_MILES: Final = 0.621371  # Type annotation is optional

class Foo:
    def __init__(self):
        self.bar: Final = "baz"   # Final instance attributes only allowed in __init__

Please note that like other typing hints, these do not prevent you from overriding the types, but they do help linters or IDEs warn you about incorrect type usage.