class A:
    def __init__(self, x):
        self.x = x
    def __call__(self):
        return self.x
class B:
    def __init__(self, x):
        self.x = x
    def method(self):
        return self.x
class C:
    def __init__(self, x=3):
        self.x = x
    def __repr__(self):
        return str(self.x)

a = A(1)
b = B(2)
c = C(3)
callables = # ваш код
print([act() for act in callables])

#Вывод:     [1, 2, 3]