Say I built some classes containing some instance methods:

class A:
    def func_of_A(self):
        print("foo")

class B:
    def func_of_B(self):
        print("bar")

How can I construct an object/variable c that is an instance of both A and B, so that I can call both c.func_of_A() and c.func_of_B()?

I could of course build a new class inheriting from A and B and make c a member of that:

class C(A,B):
    pass

c = C()

But that is not what I am looking for. I would rather not create a new class every time I am planning to use a combination of already built ones.

I could also create a function to dynamically define a new class and return an instance of it:

def merge(*inherit_from):
    class D(*inherit_from):
        pass
    return D()

c = merge(A,B)

but this is beyond cursed, because now merge(A,B), merge(A) and merge(B) all return the same type <class '__main__.merge.<locals>.D'>.

There should be an intended way to do this, shouldn't?

Is there a solution that scales well with the number of classes involved? If I already have class A1, class A2, ..., class A100 and I want to construct some c to be an instance of class A2, class A23, class A72, class A99 but not the others how would I do that? Creating a new class for every combination is pretty much impossible, given the ~2^100 combinations.

CodePudding user response：

You can use type() for that as @deceze mentioned

>>> class A:
...     def a():
...         pass
... 
>>> class B:
...     def b():
...         pass
... 
>>> def merge(name: str, *parents):
...     return type(name, parents, dict())
... 
>>> C = merge("C", A, B)
>>> C.a()
>>> C.b()
>>>