what does "/" mean as a parameter of __init__() of a Python class

Question

class MyClass(Generic[T]):
    def __init__(
        self,
        name: str,
        func: Callable[..., T],
        /,
        *args: Any,
        **kwargs: Any,
    ) -> None:
        # the function does not reference or use the "/" in any way 

what does the "/" do in this case? Does it have any special meaning or purpose?

Answer 1

It means that anything before the slash, must be passed as positional arguments (PEP 457). You can also see asterisks in arguments. Anything after the asterisks must be passed as keyword argument (PEP 3102). Python documentation about "Special parameters"

def func(a, /):
    return a

# Passing as a positional argument
func(1)  # Good
# Passing as a keyword argument
func(a=1)  # TypeError: func() got some positional-only arguments passed as keyword arguments: 'a'

#               Positional or keyword
#                         │
#     Positional only     │            ┌─Keyword only
#         ┌──┴───┐     ┌──┴───┐     ┌──┴──┐
def func2(pos_only, /, anything, *, kw_only):
    return pos_only, anything, kw_only

func2(1, 2, kw_only=3)  # Good
func2(1, anything=2, kw_only=3)  # Good
func2(pos_only=1, anything=2, kw_only=3)  # TypeError: func2() got some positional-only arguments passed as keyword arguments: 'pos_only'
func2(1, 2, 3)  # TypeError: func2() takes 2 positional arguments but 3 were given