Being stricter with Any

[pycaw]

I would like this to report an error:

from typing import  Any, cast

def a(n: int):
    pass

b: Any = 0  # or b: Any = ""
a(b)

And require an explicit cast for example:

a(cast(int, b))

I found no mention of this among the configurations. Mypy not different either. Is this impossible currently to detect and enforce?

[Eric Traut (erictraut)]

The Python type system is, by design, a gradual type system. Any plays a special role in a gradual type system, and it's described in detail in the typing spec. Pyright and mypy (and other conformant type checkers like pyrefly and ty) treat Any in the manner described in the spec. For more details about how a gradual type system is intended to work — and the role that Any plays in this, refer to this section of the typing spec.

It wouldn't be appropriate for a type checker to generate an error for a(b) because it doesn't violate any typing rules.

If you want to generate a type error here, you should not use Any as the annotation for b.

[pycaw]

Your are on point totally but the answer -- that I had to accept -- outlines the obvious method to solve this issue. Using object as a type annotation as opposed to defaulting to Any might need a marketing campaign of its own.

[Brian Schubert (brianschubert)]

object may have a meaning closer to what you're looking for:

def a(n: int) -> None: ...

def foo(b: object) -> None:
    a(b)  # E: Argument of type "object" cannot be assigned to parameter "n" of type "int" in function "a"

foo(1)   # ok
foo("")  # ok

For more on how object vs Any differ, you can refer to

• https://mypy.readthedocs.io/en/latest/dynamic_typing.html#any-vs-object
• https://stackoverflow.com/q/39817081/11082165
• https://typing.python.org/en/latest/guides/writing_stubs.html#using-any-and-object

[pycaw]

I didn't even think of using object, it's seldom used like this -- or, Any is overused. My problem X (this issue being Y) involves recursive operations on dict[str, Any] objects and using dict[str, object] instead does produce the error I am looking for. Thanks!