Question

Is there any significant difference between:

from time import time
start = time()
# some process
print time() - start

and:

from timeit import timeit
def my_funct():
    # some process
print timeit(my_funct, number=1)

For an example, I’ll use Project Euler 1 (because it’s really easy to understand/solve)

def pE1test1(): # using time()
    from time import time
    start = time()
    print sum([n for n in range(1, 1000) if n%3==0 or n%5==0])
    print time() - start

def pE1test2(): # using timeit
    print sum([n for n in range(1, 1000) if n%3==0 or n%5==0])

from timeit import timeit
pE1test1()
print timeit(pE1test2, number=1)

This outputs:

>>> 
233168
0.0090000629425
233168
0.00513921300363

What is the major difference between timeit and time?

Answer 1

timeit will use the best available timing function on your system. See the docs on timeit.default_timer.

Also, timeit turns off the garbage collector.

Also, I believe you’re using timeit wrong. You should be passing a string as per the last example in the documentation:

print timeit("pE1test2()","from __main__ import PE1test2",number=1)

And of course, another major difference is that timeit makes it trivial to time the execution of the function for thousands of iterations (which is the only time a timing result is meaningful). This decreases the importance of a single run taking longer than the others (e.g. due to your system resources being hogged by some other program).