Partial method application

p.py

import functools

class B():
    def __init__(self, n):
        self.n = n
    def __call__(self):
        print(self.n)

class A():

    def __init__(self, b):
        self.b = b

    def f(self):
        self.b()

b1 = B(3)
b2 = B(5)

a1 = A(b1)
a2 = A(b2)

f1 = functools.partial(A.f, a1)

f1()