Timeit in Python with Examples

This article will introduce you to a method of measuring the execution time of your python code snippets.
We will be using an in-built python library timeit.

This module provides a simple way to find the execution time of small bits of Python code.

Why timeit?

  • Well, how about using simple time module? Just save the time before and after the execution of code and subtract them! But this method is not precise as there might be a background process momentarily running which disrupts the code execution and you will get significant variations in running time of small code snippets.
  • timeit runs your snippet of code millions of time (default value is 1000000) so that you get the statistically most relevant measurement of code execution time!
  • timeit is pretty simple to use and has a command line interface as well as a callable one.

So now, let’s start exploring this handy library!

The module function timeit.timeit(stmt, setup, timer, number) accepts four arguments:

  • stmt which is the statement you want to measure; it defaults to ‘pass’.
  • setup which is the code that you run before running the stmt; it defaults to ‘pass’.
    We generally use this to import the required modules for our code.
  • timer which is a timeit.Timer object; it usually has a sensible default value so you don’t have to worry about it.
  • number which is the number of executions you’d like to run the stmt.

Where the timeit.timeit() function returns the number of seconds it took to execute the code.

Example 1

Let us see a basic example first.

# importing the required module
import timeit
# code snippet to be executed only once
mysetup = "from math import sqrt"
# code snippet whose execution time is to be measured
mycode = '''
def example():
    mylist = []
    for x in range(100):
# timeit statement
print timeit.timeit(setup = mysetup,
                    stmt = mycode,
                    number = 10000)

  • The output of above program will be the execution time(in seconds) for 10000 iterations of the code snippet passed to timeit.timeit() function.

    Note: Pay attention to the fact that the output is the execution time of number times iteration of the code snippet, not the single iteration. For a single iteration exec. time, divide the output time by number.

  • The program is pretty straight-forward. All we need to do is to pass the code as a string to the timeit.timeit() function.
  • It is advisable to keep the import statements and other static pieces of code in setup argument.

Example 2

Let’s see another practical example in which we will compare two searching techniques, namely, Binary search and Linear search.
Also, here I demonstrate two more features, timeit.repeat function and calling the functions already defined in our program.

# importing the required modules
import timeit
# binary search function
def binary_search(mylist, find):
    while len(mylist) > 0:
        mid = (len(mylist))//2
        if mylist[mid] == find:
            return True
        elif mylist[mid] < find:
            mylist = mylist[:mid]
            mylist = mylist[mid + 1:]
    return False
# linear search function
def linear_search(mylist, find):
    for x in mylist:
        if x == find:
            return True
    return False
# compute binary search time
def binary_time():
    SETUP_CODE = '''
from __main__ import binary_search
from random import randint'''
    TEST_CODE = '''
mylist = [x for x in range(10000)]
find = randint(0, len(mylist))
binary_search(mylist, find)'''
    # timeit.repeat statement
    times = timeit.repeat(setup = SETUP_CODE,
                          stmt = TEST_CODE,
                          repeat = 3,
                          number = 10000)
    # priniting minimum exec. time
    print('Binary search time: {}'.format(min(times)))        
# compute linear search time
def linear_time():
    SETUP_CODE = '''
from __main__ import linear_search
from random import randint'''
    TEST_CODE = '''
mylist = [x for x in range(10000)]
find = randint(0, len(mylist))
linear_search(mylist, find)
    # timeit.repeat statement
    times = timeit.repeat(setup = SETUP_CODE,
                          stmt = TEST_CODE,
                          repeat = 3,
                          number = 10000)
    # priniting minimum exec. time
    print('Linear search time: {}'.format(min(times)))  
if __name__ == "__main__":

  • The output of above program will be the minimum value in the list times.
    This is how a sample output looks like:
  • timeit.repeat() function accepts one extra argument, repeat. The output will be a list of the execution times of all code runs repeated a specified no. of times.
  • In setup argument, we passed:
    from __main__ import binary_search
    from random import randint

    This will import the definition of function binary_search, already defined in the program and random library function randint.

  • As expected, we notice that execution time of binary search is significantly lower than linear search!

Example 3
Finally, I demonstrate below how you can utilize the command line interface of timeit module:


Here I explain each term individually:

So, this was a brief yet concise introduction to timeit module and its practical applications.
Its a pretty handy tool for python programmers when they need a quick glance of the execution time of their code snippets.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

This article is attributed to GeeksforGeeks.org



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