Generators versus iterators.

benchmark_generators.py

def a(n):
   for i in xrange(n):
       yield i

def b(n):
    r = []
    for i in xrange(n):
        r.append(i)
    return r

def numerate(fn, n):
    for i in fn(n):
        pass

# >>> %timeit numerate(a, 1000)
# 10000 loops, best of 3: 112 us per loop
#
# >>> %timeit numerate(b, 1000)
# 10000 loops, best of 3: 155 us per loop
#
# >>> %timeit numerate(a, 10000)
# 1000 loops, best of 3: 1.11 ms per loop
#
# >>> %timeit numerate(b, 10000)
# 1000 loops, best of 3: 1.54 ms per loop

gistfile2.txt