class A:
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def add(self):
        return self.a + self.b

    def sub(self):
        return self.a - self.b
    
a = A(1, 2)
assert a.add() == 3
assert a.sub() == -1

assert A.__base__ is object

class B(A):
    def __init__(self, a, b, c):
        super(B, self).__init__(a, b)
        self.c = c

    def add(self):
        return self.a + self.b + self.c

    def sub(self):
        return self.a - self.b - self.c

assert B.__base__ is A    

b = B(1, 2, 3)
assert b.add() == 6
assert b.sub() == -4

class C(B):
    def __init__(self, a, b, c, d):
        super(C, self).__init__(a, b, c)
        self.d = d

    def add(self):
        return self.a + self.b + self.c + self.d

    def sub(self):
        return self.a - self.b - self.c - self.d
    
assert C.__base__ is B

c = C(1, 2, 3, 4)
assert c.add() == 10
assert c.sub() == -8

class D(C):
    def __init__(self, a, b, c, d, e):
        super(D, self).__init__(a, b, c, d)
        self.e = e

    def add(self):
        return super(D, self).add() + self.e

    def sub(self):
        return super(D, self).sub() - self.e
    
assert D.__base__ is C

d = D(1, 2, 3, 4, 5)
assert d.add() == 15
assert d.sub() == -13

assert isinstance(1, int)
assert isinstance(1, object)
assert isinstance(C, type)
assert isinstance(C, object)
assert isinstance(d, object)
assert isinstance(d, C)
assert isinstance(d, B)
assert isinstance(d, A)
assert isinstance(object, object)
assert isinstance(type, object)

assert isinstance(1, (float, int))
assert isinstance(1, (float, object))
assert not isinstance(1, (float, str))
assert isinstance(object, (int, type, float))
assert not isinstance(object, (int, float, str))

try:
    isinstance(1, (1, 2))
    exit(1)
except TypeError:
    pass

try:
    isinstance(1, 1)
    exit(1)
except TypeError:
    pass

class A:
    a = 1
    b = 2

assert A.a == 1
assert A.b == 2

class B(A):
    b = 3
    c = 4

assert B.b == 3
assert B.c == 4

assert B.a == 1

class A:
    x = 1
    x = x + 1
    y = 1
    z = x + y

assert A.x == 2
assert A.y == 1
assert A.z == 3

class MyClass:
    a = 1,2,3
    b, c = 1, 2
    d = b + c

assert MyClass.a == (1, 2, 3)
assert MyClass.b == 1
assert MyClass.c == 2
assert MyClass.d == 3