NotFoundLookupError when using dispatch.multi in class method

master 7e9b8657

from plum import dispatch

@dispatch.multi((int, str), (int, int))
def f(x: int, y: {int, str}):
    print(f'{x}, {y}')

class C():
    @dispatch
    def g(self, x: int, y: int):
        print(f'{x}, {y}')

    @dispatch
    def g(self, x: int, y: str):
        print(f'{x}, {y}')

    @dispatch.multi((int, str), (int, int))
    def h(self, x: int, y: {int, str}):
        print(f'{x}, {y}')

f(3, 4) # OK

c = C()
c.g(3, 4) # OK
c.g(3, 'cat') # OK

c.h(3, 4) # NotFoundLookupError
c.h(3, 'cat') # NotFoundLookupError

I did not yet try this on the latest released branch.

[jlapeyre]

Thanks. Your last example has solved my problem.

[wesselb]

Ah, sorry, I should have said that this should also be used when classes are used, even if you don’t make use of inheritance. The problem is that vanilla functions and methods of classes behave slightly differently.

Plum should play nicely with ABC. Here’s an example:

import abc

from plum import Dispatcher, Referentiable, Self

class A(metaclass=Referentiable(abc.ABCMeta)):
    @abc.abstractmethod
    def f(self, x):
        pass

class B(A):
    _dispatch = Dispatcher(in_class=Self)

    @_dispatch
    def f(self, x: int):
        return x

>>> A()
TypeError: Can't instantiate abstract class A with abstract methods f

>>> b = B()

>>> b.f(1)
1

>>> b.f("1")
NotFoundLookupError: For function "f" of <class '__main__.B'>, signature (builtins.str) could not be resolved.