How to Sleep in Python (adding delays)

Python provides several sleep functions that allow us to add delays to our code. Let’s explore the time.sleep(), asyncio.sleep(), and sched.scheduler.enter() functions to achieve this functionality.

1. Using time.sleep()

import time

print("Starting sleep for 5 seconds")
time.sleep(5)
print("Waking up after 5 seconds")

The time.sleep() function is a fairly straightforward way to add delays to our Python code.

It takes in one argument, the number of seconds to sleep, which can be a decimal or integer value.

This function will block the execution of the program, meaning it will wait for the specified time before continuing.

An InterruptedError exception will be raised if the sleep is interrupted by some signal.

2. Using asyncio.sleep()

import asyncio

async def delay_print(delay, message):
    await asyncio.sleep(delay)
    print(message)

async def main():
    print("Starting sleep for 5 seconds")
    await delay_print(5, "Waking up after 5 seconds")

asyncio.run(main())

asyncio.sleep() is similar to time.sleep(), but it’s used in asynchronous programming.

This function also takes in a single argument representing the number of seconds to sleep.

While time.sleep() is blocking, asyncio.sleep() is non-blocking, meaning it will allow the rest of our program to continue while it waits for the specified time.

This function is best used for longer delays, especially in asynchronous programs where we might wait for a task to complete without blocking the event loop. It returns a coroutine, which can be awaited.

3. Using sched.scheduler.enter()

import sched, time

s = sched.scheduler(time.time, time.sleep)

def delay_print(sc, delay, message):
    print(message)
    s.enter(delay, 1, delay_print, (sc, delay, message))

print("Starting sleep for 5 seconds")
s.enter(5, 1, delay_print, (s, 5, "Waking up after 5 seconds"))
s.run()

The sched.scheduler.enter() function is a slightly more complex but more powerful way to schedule events.

This one takes multiple arguments, including the time to enter the event, the priority, and the function to call when the event occurs.

sched.scheduler.enter() is also non-blocking and can be used to schedule events at specific times.