No overload variant of "apply" of "Styler" matches argument types "Callable[[Series[int], str], list[str]]", "str", "int" about pandas-stubs HOT 2 CLOSED

Thanks for the report. This is non-trivial to fix. We have overloads that test whether you are passing a Callable that takes a Series or DataFrame, as that pairs with the axis argument of Styler.apply(). But there really aren't signatures for callables that have keyword arguments, and the recommended way to handle that is to use Protocol. But that has issues - see microsoft/pyright#7898 because it forces the callable to have a specific name for the first argument.

I'll have to see what the typing experts have to say about this.

from pandas-stubs.

I found a fix based on the response to the pyright issue I reported. However, it will require you to change the declaration of your function to be:

def highlight_max(x: 'pd.Series[int]', /, color: str) -> List[str]:
    """Highlight max."""
    return [f"color: {color}" if val == x.max() else "" for val in x]

The / in the function declaration tells the type checker that color is a keyword argument, while the first argument is positional.

from pandas-stubs.