ruff/crates/red_knot_python_semantic/resources/mdtest/annotations/any.md

Any

Annotation

typing.Any is a way to name the Any type.

from typing import Any

x: Any = 1
x = "foo"

def f():
    reveal_type(x)  # revealed: Any

Aliased to a different name

If you alias typing.Any to another name, we still recognize that as a spelling of the Any type.

from typing import Any as RenamedAny

x: RenamedAny = 1
x = "foo"

def f():
    reveal_type(x)  # revealed: Any

Shadowed class

If you define your own class named Any, using that in a type expression refers to your class, and isn't a spelling of the Any type.

class Any: ...

x: Any

def f():
    reveal_type(x)  # revealed: Any

# This verifies that we're not accidentally seeing typing.Any, since str is assignable
# to that but not to our locally defined class.
y: Any = "not an Any"  # error: [invalid-assignment]

Subclass

The spec allows you to define subclasses of Any.

TODO: Handle assignments correctly. Subclass has an unknown superclass, which might be int. The assignment to x should not be allowed, even when the unknown superclass is int. The assignment to y should be allowed, since Subclass might have int as a superclass, and is therefore assignable to int.

from typing import Any

class Subclass(Any): ...

reveal_type(Subclass.__mro__)  # revealed: tuple[Literal[Subclass], Any, Literal[object]]

x: Subclass = 1  # error: [invalid-assignment]
# TODO: no diagnostic
y: int = Subclass()  # error: [invalid-assignment]

def _(s: Subclass):
    reveal_type(s)  # revealed: Subclass

Invalid

Any cannot be parameterized:

from typing import Any

# error: [invalid-type-form] "Type `typing.Any` expected no type parameter"
def f(x: Any[int]):
    reveal_type(x)  # revealed: Unknown