class Tmp:
    common_t = None  # class variable

    def __init__(self, t):
        self.t = t  # instance variable


Tmp.common_t = [1, 2]
print(Tmp.common_t)
t1 = Tmp([1, 2, 3])
t2 = Tmp([4, 5, 6])
t1 = t2
t1.t[0] = 0
t2.t[1] = 0
print(t1.t)
print(t2.t)
print(Tmp.common_t)
t1.__class__.common_t.append(3)
print(Tmp.common_t)