Can a function with keyword arguments be decorated with @multimethod?

[alzuse]

For example, I have the following code:

class Foo:
    @multimethod
    def call_n(self, name: str, nets: str):
        print(f"NETS")

    @call_n.register
    def call_n2(self, name: str, *, prefix: Union[str, int] = "",  suffix: Union[str, int] = ""):
        print("PS")
    
    @call_n.register
    def call_n3(self, name: str, func: types.FunctionType):
        print("FUNC:", func(name))

How can we distinguish between call_n and call_n2 when making a call?

[coady]

As is, called with a positional func works:

Foo().call_n('', lambda s: s)

Using @multidispatch instead of @multimethod also supports keyword arguments:

Foo().call_n('', func=lambda s: s)

[alzuse]

As is, called with a positional func works:

Foo().call_n('', lambda s: s)
Using @multidispatch instead of @multimethod also supports keyword arguments:

Foo().call_n('', func=lambda s: s)

Could you please give an example of multidispatch? In the above example, I directly changed multimethod to multidispatch and then call,

from multimethod import multimethod, multidispatch
from typing import Union
import types

class Foo:
    # @multimethod
    @multidispatch
    def call_n(self, name: str, nets: str):
        print(f"NETS")

    @call_n.register
    def call_n2(self, name: str, *, prefix: Union[str, int] = "",  suffix: Union[str, int] = ""):
        print("PS")
    
    @call_n.register
    def call_n3(self, name: str, func: types.FunctionType):
        print("FUNC:", func(name)
ff = Foo()
ff.call_n("A", "A1")
ff.call_n("A", prefix="X", suffix="0")
ff.call_n("A", func=lambda x: x + "0"

but it reported errors as follows:

Traceback (most recent call last):
  File "/path/foo2.py", line 20, in <module>
    ff.call_n("A", "A1")
    ~~~~~~~~~^^^^^^^^^^^
  File ".../multimethod.py", line 410, in __call__
    func = self.dispatch(*params)
  File ".../multimethod.py", line 340, in dispatch
    return self[types]
           ~~~~^^^^^^^
  File ".../multimethod.py", line 335, in __missing__
    return self.setdefault(types, self.select(types, self.parents(types)))
                                  ~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".../multimethod.py", line 327, in select
    raise DispatchError(f"{self.__name__}: {len(keys)} methods found", types, keys)
multimethod.DispatchError: ('call_n: 0 methods found', (<class '__main__.Foo'>, <class 'str'>, <class 'str'>), set())

[coady]

Try it with a base/stub implementation:

class Foo:
    @multidispatch
    def call_n(self, name): ...

    @call_n.register
    def call_n1(self, name: str, nets: str):
        print(f"NETS")

    ...

multidispatch mimics functools.singledispatch by ignoring the annotations in the initial definition. I don't particularly like that behavior, but it was designed to be compatible.

And this is only relevant for keyword argument dispatching. Your original post with @multimethod works.