Liskov Substitution

#theory #code

class T1:
    ...

class T2(T1):
    ...

def f1(p: T1) -> None:
    ...

o2 = T2()

f1(o2)  # OK

• Liskov substitution say that every object t2 subclass of t1, where t1 is accepted, t2 will be accepted as well. But the opposite is not true because t2 can implement additional methods, so t1 cannot be used in the place where t2 is accepted.