Kodeclik Blog
Measuring Elapsed Time in Python
Would you like to time your Python program to see how fast it runs? Learn about ways to measure elapsed time!
In this blogpost, we will learn about 3 different modules to help measure elapsed time in Python.
Method 1: Use the time module
The time module has a method called time() which returns the seconds since the beginning of the “epoch” (which is a system dependent time, but because it is fixed for your program, it serves the purpose of calculating elapsed time). Thus, we can invoke this method two times, once before the body of code we are timing and once after the body of code and we can subtract these two values to measure the elapsed time.
Here is a simple Python program to compute the elapsed time.
import time as t
start_time = t.time()
x=0
for i in range(1000000):
x = x+1
end_time = t.time()
print("That took - ",end_time-start_time, "seconds.")A sample output of the program will be:
That took - 0.8412454128265381 seconds.Your specific numbers might vary. For instance when we run this program five times, here are the outputs we observed:
That took - 0.8405888080596924 seconds.
That took - 0.8721990585327148 seconds.
That took - 0.76426100730896 seconds.
That took - 0.754683256149292 seconds.
That took - 0.7951443195343018 seconds.For this program, we are artificially running a loop for a million iterations (else the timer’s value would be really small). If you would like increased resolution, there is another method called “time_ns” which returns its value in nanoseconds since the epoch. Here is a modification to our earlier program that uses this method:
import time as t
start_time = t.time_ns()
x=0
for i in range(1000000):
x = x+1
end_time = t.time_ns()
print("That took - ",end_time-start_time, "nanoseconds.")A sample output is:
That took - 831961242 nanoseconds.Method 2: Use the timeit module
The timeit module is similar to time but its methods are named different. Here is how a timer program will look using this module (note that we have also modified the program to compute the sum of integers, so the times measured will be different):
import timeit as t
start_time = t.default_timer()
x=0
for i in range(1000000):
x = x+i
end_time = t.default_timer()
print("That took - ",end_time-start_time, "seconds.")The output is:
That took - 1.188822557000094 seconds.Again the results will be different for your computer and operating environment, and across different runs.
Method 3: Use the datetime module
The final method we would like to showcase is the datetime module. Unlike the first two methods, the datetime module gives the time in terms of days, hours, minutes, and seconds. As a result this module is more suitable for timing programs that run over multiple days or hours and where a user-friendly output is necessary.
Here is a program that uses the Datetime module. Note that we are also printing the start and end time using the datetime module’s format.
from datetime import datetime as d
start_time = d.now()
print("Start time is:", start_time)
x=0
for i in range(1000000):
x = x+i
end_time = d.now()
print("End time is:", end_time)
print("That took - ",end_time-start_time, "seconds.")The output is:
Start time is: 2022-02-20 01:39:29.007944
End time is: 2022-02-20 01:39:29.925314
That took - 0:00:00.917370 seconds.Note that the start time and end time give all the day/hour/minute/second information and you are able to subtract start_time from end_time to obtain the second information.
We have seen three different methods for measuring elapsed time in your Python programs. Which one is your favorite?
Interested in more things Python? See our blogpost on Python's enumerate() capability. Also if you like Python+math content, see our blogpost on Magic Squares. Finally, master the Python print function!
Want to learn Python with us? Sign up for 1:1 or small group classes.
