import datetime
t1 = datetime.date(2021, 3, 5) - datetime.date(2021, 2, 23)
t2 = datetime.date(2020, 3, 5) - datetime.date(2020, 2, 23)
print((t2 - t1).days)

class A:
    def f(self):
        print('A', end="")
class B:
    def f(self):
        print('B', end="")
class C(A):
    def f(self):
        print("C", end="")
        super().f()
        self.__class__.__bases__ = (B,)
x = C()
_ = x.f(), x.f()

class B:
    def __init__(self) : 
        print ('В', end='')
        super().__init__()
class C:
    def __init__(self): 
        print('C', end='')
        super().__init__ ()
class D(B, C):
    def __init__(self):
        print('D', end='') 
        B.__init__(self)
        C.__init__(self)
X = D()

class A:
    def f(self):
        print("A", end="")
class B(A):
    def f(self):
        print("B", end="")
        super().f()
        A.f(self)
class C(A):
    def f(self):
        print("C", end="")
        super().f()
        A.f(self)
class D(B, C):
    def f(self):
        print("D", end="")
        super().f()
d = D()
d.f()

d = {}
d[2, 3] = "a", "b"

class A:
    x = 1
    l = []
a1, a2 = A(), A()
a1.x = 2
a1.l.append(100)
print(a2.x, len(a2.l))

class C:
    listing = []  
    
x = C()  
x.listing.append(1)
x.listing.append(1)
x.listing = 1
print(x.listing, C.listing)

def f():
    setattr(f, "x", getattr(f, "x", 0) + 1)
    f.f = f
    return f
x = f()()().f.f.f().f.x
print(x)

class A:
    __x = 1

a = A()

class A:
    __x = 1
    def f(self):
        return "f from A"
    
    def g(self):
        return "g from A"

class B:
    __x = 2
    def f(self):
        return "f from B"
    
    def g(self):
        return "g from B"

class C(A, B):
    f = B.f
    
c = C()
print(c.f(), c.g(), c._A__x, c._B__x)