singledispatch_next.py

from functools import singledispatch


def singledispatch_next(f):
    """
    Decorate a `singledispatch` function f with a `next` method.

    `f.next(__class__)` dispatches to the 'base' or next implementation in
    the __class__'s mro chain.

    Example
    -------
    >>> @singledispatch_next
    ... @singledispatch
    ... def func(a):
    ...     print("In default func impl.")
    ...
    >>> @func.register(int)
    ... def func_int(a):
    ...    print("In func_int.")
    ...    func.next(int)(a)
    ...
    >>> func(1)
    In func_int.
    In default func impl.
    """
    def next_(cls):
        mro = cls.mro()
        if len(mro) > 1:
            return f.dispatch(mro[1])
        else:
            raise TypeError(f"{cls} has no next")
    f.next = next_
    return f

@singledispatch_next
@singledispatch
def f(a):
    print("Im", a)


@f.register(int)
def fi(a):
    print("Im a int", a)

@f.register(bool)
def fb(a):
    f.next(bool)(a)
    print("Im an int too", a)



f("")
f(1)
f(True)

print(f.dispatch(bool.mro()[1]))