Python Type Hint Syntax Error. Need help for "Optional[Tuple[int, set[int]]]"

[Bat-Script]

🏷️ Discussion Type

Bug

Body

Today while upgrading my Python environment... and I encountered a type hint issue that's causing errors in my IDE! Here's the problematic code:

in_switch: Optional[Tuple[int, set[int]]] = None

and on here:

items: Optional[List["Expr"]] = None

My IDE (PyCharm) is showing an error message:

Invalid type argument 
Inspection info: Reports invalid usages of type hints.

I've tried searching for solutions but I'm stuck...
What's wrong with this syntax?
How can I fix it properly?
If this is Python version dependent, what's the most compatible way to write this that works across all Python 3 versions?

The IDE's inspection info shows examples like:

from typing import TypeVar
T0 = TypeVar('T1')  # Error: Argument of 'TypeVar' must be 'T0'

def b(p: int) -> int:  # Error: Type specified both in comment and annotation
    # type: (int) -> int
    pass

But none of these seem to match my case directly really...

Any help would be greatly appreciated! :)

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[jgschmitz]

The issue is that you're mixing type-hint syntax from different Python versions.

This part:

set[int]

only works in Python 3.9+.

So this is valid in Python 3.9+:

from typing import Optional, Tuple

in_switch: Optional[Tuple[int, set[int]]] = None

But if your interpreter or IDE is configured for Python 3.8 or older, set[int] is invalid as a type hint.

Use Set from typing for wider compatibility:

from typing import Optional, Tuple, Set

in_switch: Optional[Tuple[int, Set[int]]] = None

Similarly, this is already the compatible form:

from typing import Optional, List

items: Optional[List["Expr"]] = None

If you want the most compatible Python 3 style, write both like this:

from typing import List, Optional, Set, Tuple

in_switch: Optional[Tuple[int, Set[int]]] = None
items: Optional[List["Expr"]] = None

If you're using Python 3.10+, you can also write the newer style:

in_switch: tuple[int, set[int]] | None = None
items: list["Expr"] | None = None

So the problem is most likely not Optional or Tuple; it is set[int] being used while PyCharm is configured for a Python version before 3.9.

Check your PyCharm project interpreter / language level. If it is set to Python 3.8 or older, either upgrade it or use typing.Set.