You can use Python’s sleep() function to add a time delay to your code.
This function is handy if you want to pause your code between API calls, for example. Or enhance the user’s experience by adding pauses between words or graphics.
from time import sleep
sleep(2)
print("hello world")
When I run the above code, there’s about a two-second delay before "hello world" prints.
I experience a delay because sleep() stops the “execution of the calling thread” for a provided number of seconds (though the exact time is approximate). So the execution of the program is paused for about two seconds in the above example.
In this article, you’ll learn how to put your Python code to sleep.
The Details of Sleep
Python’s time module contains many time-related functions, one of which is sleep(). In order to use sleep(), you need to import it.
from time import sleep
sleep() takes one argument: seconds. This is the amount of time (in seconds) that you want to delay your code.
seconds = 2
sleep(seconds)
Sleep in Action
Now let’s use sleep() in a few different ways.
After I import the sleep from the time module, two lines of text will print. However, there will be an approximate two-second delay between the printing of each line.
from time import sleep
print("Hello")
sleep(2)
print("World")
This is what happened when I ran the code:
"Hello" This line printed right away.
Then, there was approximately a two-second delay.
"World" This line printed about two seconds after the first.
You Can Be Precise
Make your time delay specific by passing a floating point number to sleep().
from time import sleep
print("Prints immediately.")
sleep(0.50)
print("Prints after a slight delay.")
This is what happened when I ran the code:
"Prints immediately." This line printed immediately.
Then, there was a delay of approximately 0.5 seconds.
"Prints after a slight delay." This line printed about 0.5 seconds after the first.
Create a Timestamp
Here’s another example to consider.
In the code below, I create five timestamps. I use sleep() to add a delay of approximately one second between each timestamp.
import time
for i in range(5):
current_time = time.localtime()
timestamp = time.strftime("%I:%m:%S", current_time)
time.sleep(1)
print(timestamp)
Here, I import the entire time module so I can access multiple functions from it, including sleep().
import time
Then, I create a for loop that will iterate five times.
for i in range(5):
...
On each iteration, I get the current time.
current_time = time.localtime()
I get a timestamp using another function in the time module, strftime().
timestamp = time.strftime("%I:%m:%S", current_time)
The sleep() function is next, which will cause a delay on each iteration of the loop.
time.sleep(1)
When I run the program I wait about a second before the first timestamp prints out. Then, I wait about a second for the next timestamp to print, and so on until the loop terminates.
The output looks like this:
04:08:37
04:08:38
04:08:39
04:08:40
04:08:41
sleep() and the User Experience
Another way to use sleep() is to enhance the user’s experience by creating some suspense.
from time import sleep
story_intro = ["It", "was", "a", "dark", "and", "stormy", "night", "..."]
for word in story_intro:
print(word)
sleep(1)
Here, I iterate through the list of words in story_intro. To add suspense, I use the sleep() function to delay by about a second after each word is printed.
time.sleep(1)
Although execution speed is often at the forefront of our minds, sometimes it’s worth slowing down and adding a pause in our code. When those occasions arise, you know what to reach for and how it works.
I write about learning to program, and the best ways to go about it on amymhaddad.com. I tweet about programming, learning, and productivity: @amymhaddad.