Python: iterating over list vs over dict items efficiency

Question

Is iterating over some_dict.items() as efficient as iterating over a list of the same items in CPython?

Answer 1

A little benchmark shows me that iterating a list is definately faster.

def iterlist(list_):
    i = 0
    for _ in list_:
        i += 1
    return i

def iterdict(dict_):
    i = 0
    for _ in dict_.iteritems():
        i += 1
    return i

def noiterdict(dict_):
    i = 0
    for _ in dict_.items():
        i += 1
    return i

list_ = range(1000000)
dict_ = dict(zip(range(1000000), range(1000000)))

Tested with IPython on Python 2.7 (Kubuntu):

%timeit iterlist(list_)
10 loops, best of 3: 28.5 ms per loop

%timeit iterdict(dict_)
10 loops, best of 3: 39.7 ms per loop

%timeit noiterdict(dict_)
10 loops, best of 3: 86.1 ms per loop