Python - mutable "static" variable

class Test:
    i = [3]

t = Test()
print(t.i) # [3]

t.i[0] = 5
print(Test.i) # [5]
print(t.i) # [5]

Test.i[0] = 6
print(t.i) # [6]

print(Test.i) # [6]

u = Test()
print(u.i) # [6]

print(Test.__dict__) # {'i': [6], ...}
print(t.__dict__) # {}
print(u.__dict__) # {}