mutable_int.py

class MutableInt:

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

    def __iadd__(self, other):
        self.value += other
        return self

    def __imul__(self, other):
        self.value *= other
        return self

    def magic_op(self, method, other):
        cls = type(self)
        if isinstance(other, cls):
            other = other.value
        res = getattr(self.value, method)(other)
        if isinstance(res, int) and not isinstance(res, bool):
            res = cls(res)
        return res

    def __int__(self):
        return self.value

    def __add__(self, other):
        return self.magic_op('__add__', other)

    def __mul__(self, other):
        return self.magic_op('__mul__', other)

    def __eq__(self, other):
        return self.magic_op('__eq__', other)

    # other methods like __sub__, __pow__, etc are required for full compatibility with ints:
    # https://docs.python.org/3/reference/datamodel.html#emulating-numeric-types


a = MutableInt(1)
b = MutableInt(2)

a = b
print(a == 2)  # True
b += 1
print(a.value)  # 3
print(b.value)  # 3
print(a == 3)  # True
print(b == 3)  # True
a *= 4
print(a == 12)  # True
print(b == 12)  # True