Cannot append to a returned list?

Question

def f():
    lst = ['a', 'b', 'c']
    return lst[1:]

why is f().append('a') is None == True even though f().__class__ is <type 'list'> and f() == ['b', 'c']

Answer 1

Because append() returns None and not the list object. Use

l = f()
l.append('a')
...