Python Timeit() with Examples

The Python timeit module is specially designed to find out the precise execution time of a code snippet. Here in this Python tutorial, we will walk you through how to use the built-in Python library timeit with the help of some examples. timeit is an inbuilt Python module that can evaluate the execution time of a code snippet or program. Although Python also has a datetime module, where we can use its time method before and after a code snippet and find the execution time of the code, this approach is not precise as there are many other background processes that can distort the results.

Python timeit.timeit() Function

timeit() is a method of the Python timeit module, and it returns the execution time of the code snippet in seconds. The timeit() method accepts the Python code snippet in a string and executes it 1 million times, and returns the total execution time by executing the code snippet 1 million times. It is the default number of executions that you can also change if you want.

Python timeit() method syntax:

 timeit.timeit(stmt, setup, timer, number)

timeit() Method Parameters

Python timeit() Method Examples

Example 1: Execute the code 1 million times.

import timeit

#code snippet
code =  "[i for i in range(199)]"

execution_time = timeit.timeit(stmt = code)

#execution time of code by 1,000,000
print(execution_time, "seconds" )

Output

7.756799300000001 seconds

The above result does not show the execution time of a single code snippet. It shows the execution time of the code 1 million times. Note: The timeit() method returns the time of executing the code 1 million times. To find out the best execution time, divide the output by 1 million, or set the number parameter to 1. Example 2: Execute the code only one time.

import timeit

#code snippet
code =  "[i for i in range(199)]"

#execute the code 1 time
execution_time = timeit.timeit(stmt = code, number =1)

print(execution_time, "seconds" )

Output

1.2000000000012001e-05 seconds

Here, you can see that the execution time of the code snippet is less than 1 second, and it is approximately 0 seconds. Example 3: Execution time of a multi-line Python code. By far, we only encountered examples where the code snippet is of a single line. As we also want to find out the execution time of a function or multiple lines of code. Here, we use Python multiple-line string with triple double, or single quotation marks or separate the line with semicolons. Example 3.1 : Use semicolons for multiple lines of code.

import timeit

#code snippet
code =  "a= 20;b= 35;c=39;sum= a+b+c "

#execute the code 1000 time
execution_time = timeit.timeit(stmt = code)

print("Total Execution time:",execution_time, "seconds" )

#divide the execution_time with number or 1000000 to findout the best execution time of code
print("Single Execution time:",execution_time/1000000, "seconds")

Output

Total Execution time: 0.17900560000000004 seconds
Single Execution time: 1.7900560000000004e-07 seconds

Example 3.2 : Use a multi-line string for multiple lines of code.

import timeit

#code snippet
code ="""
def sum(a,b,c):
    return a+b+c
"""

#execute the code 100000 times
execution_time = timeit.timeit(stmt = code)\

print("Total Execution time:",execution_time, "seconds" )

#divide the execution_time with number or 1000000 to find out the best execution time of code
print("Single Execution time:",execution_time/1000000, "seconds")

Output

Total Execution time: 0.09432300000000005 seconds

Single Execution time: 9.432300000000004e-08 seconds

Example 4: Measure the time of executing a function using the setup parameter. By far, we have discussed the stmt and number parameters. Let’s also use the setup parameter. The setup parameter is used to specify a code that should execute before every stmt .

import timeit

#setup code
import_math = "import math"

#code snippet
code ="""
def sum(a,b,c):
    return (math.sqrt(a) + math.sqrt(b) + math.sqrt(c))**2
"""

#execute the code 200000 times
execution_time = timeit.timeit(stmt = code, setup= import_math, number =2000000)

print("Total Execution time:",execution_time, "seconds" )

#divide the execution_time with number or 1000000 to find out the best execution time of code
print("Single Execution time:",execution_time/2000000, "seconds")

Output

Total Execution time: 0.2599065 seconds

Single Execution time: 1.2995324999999998e-07 seconds

Python Timeit default_timer() Method

The timeit.default_timer() method returns the time when it is executed. It can also be used to find out the execution time of a Python code snippet. Timeit default_timer() Examples Example 1:

import timeit

def test_func():
    return [i for i in range(100)]

first_timer =timeit.default_timer()
print(" Statemet1  Executed at:",first_timer , "sec")

test_func()

second_timer = timeit.default_timer()

print("Statemet2 Executed at:", second_timer, "sec")

print("The execution time of test_func() is:", second_timer - first_timer)

Output

Statemet1  Executed at: 0.3830903 sec

Statemet2 Executed at: 0.394941 sec

The execution time of test_func() is: 0.011850699999999992

Example 2: Delay the code execution with the Python time.sleep() method

import time
import timeit

first_timer =timeit.default_timer()
print(" Statemet1  Executed at:",first_timer , "sec")

#2 seconds delay
time.sleep(2)

second_timer = timeit.default_timer()
print("Statemet2 Executed at:", second_timer, "sec")

Output

Statemet1 Executed at: 0.376851 sec
Statemet2 Executed at: 2.4023813 sec

Python Timeit repeat() method

The timeit module has the repeat() method, which is similar to the timeit() method. However, it accepts an additional parameter called repeat . The repeat() method calls the timeit() method the number of times the repeat parameter is specified.

Python timeit repeat() method syntax

repeat(stmt, setup, timer, number, repeat)

Example

import timeit

code="""
def test_func():
    return [i for i in range(100)]
"""

#call the timeit() method 4 times
print(timeit.repeat(stmt=code, repeat=4))

Output

[0.14668000000000003, 0.11089179999999998, 0.0876074, 0.09344799999999998]

Timeit Command Line tool

The Python timeit module also provides a command-line interface to find out the execution time of a Python code snippet directly from the command prompt or terminal.

Timeit Command Line syntax

python -m timeit [-n N] [-r N] [-u U] [-s S] [-h] [statement ...]

• [-n Number] represents the number of times the code statement should execute.
• [-r Number] represents the number of times the timer should repeat. The default value is 5.
• [-s String] represents the setup parameter that will execute once before the code statement.
• [-u Unit] represents the unit of timer, namely nsec, usec, msec or sec.
• [-h] displays the help message.
• [statemet…] represents the code snippet.

Python Timeit Command Line Tool Example

Example 1

C:\Users\tsmehra>python -m timeit "[i for i in range(200)]"
50000 loops, best of 5: 4.86 usec per loop

Example 2

C:\Users\tsmehra>python -m  timeit -n 100 "[i for i in range(200)]"
100 loops, best of 5: 4.87 usec per loop

Example3

C:\Users\tsmehra>python -m  timeit -n 100 -r 10 "[i for i in range(200)]"
100 loops, best of 10: 4.84 usec per loop

Example 4

C:\Users\tsmehra>python -m  timeit -n 100 -r 10  -u sec "[i for i in range(200)]"
100 loops, best of 10: 4.69e-06 sec per loop

Summary

In this program, we saw many examples of the Python timeit() module. timeit is an inbuilt Python module that can calculate the execution time of a Python code snippet. The timeit module has three major methods, namely timeit(), default_timer(), and repeat(), which can calculate the code execution time. The Python timeit() method accepts the code as a string and returns the execution time in seconds. On the contrary, the default_timer() method returns the time of its execution. The repeat() method calls the timeit() method a number of specified times. People are also reading:

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