Inconsistent behaviour between dict.items and dict.values

Question

_{Note: code examples in python3, but the question stands for python2 as well (replacing .keys with .viewkeys, etc)}<

Answer 1

Because in a dict you can not have repeated keys values, but you can have repeated values values:

>>> d = {0: 0, 1: 0, 2: 0, 3: 0, 4: 0}
>>> d.keys()
[0, 1, 2, 3, 4]
>>> d.values()
[0, 0, 0, 0, 0]
>>> d.items()
[(0, 0), (1, 0), (2, 0), (3, 0), (4, 0)]

The keys() method return something like cuacks and ducks like a set because you can not have repeated keys on the dict, but you can have repeated values on values(). That's why keys cuacks and ducks like a set but values cuacks and ducks like a list.