Adding delays to Python's for loop can be achieved through the time.sleep() function, 1. Import the time module; 2. Call time.sleep (seconds) in the loop body, and the parameters can be integers or floating-point numbers; 3. Control the interval between each loop. Practical applications include controlling the frequency of crawler requests, hardware reading rhythm, and simulated timing tasks. Notes are: Avoid setting too short delays to reduce system overhead, sleep() accuracy is limited by the operating system, and time modules need to be imported; if more complex scheduling is required, you should consider using asyncio or threading modules.
When writing Python scripts, sometimes we want to "stop" between each loop, for example, perform an operation every few seconds. At this time, you can use time.sleep()
to achieve the delay effect.

In fact, the method is very simple: add a sleep to the for loop to control the interval time between each loop.
How to add a delay in a for loop
The Python standard library has a time
module that provides a sleep()
function. Its parameters are seconds, either integer or floating point.

Let's give a simple example:
import time for i in range(5): print(f"{i1} loop") time.sleep(2) # Wait for 2 seconds
This code pauses for 2 seconds after each print, and then continues with the next cycle.

Practical application scenarios of delay
This kind of delay loop is quite common in reality, such as:
- Avoid requests too frequently when crawling web page content
- Controls the reading frequency of hardware devices (such as sensors)
- Simulate a timed task or progress update
For example, if you are working on a crawler project and don’t want to put too much pressure on the target website, you can control the frequency like this:
import time import requests urls = ["https://example.com/page1", "https://example.com/page2", ...] for url in urls: response = requests.get(url) print(response.status_code) time.sleep(3) # Wait 3 seconds after each request
Notes and FAQs
- Don't set a delay that is too short : such as
time.sleep(0.001)
, which may cause excessive system scheduling overhead. - Precision problem : The accuracy of
time.sleep()
is not 100% accurate, especially on Windows, the minimum sleep unit may be about 15ms. - Don't forget import time : This function belongs to the time module, so it must be imported before it can be used.
If you need more complex scheduling methods, such as performing multiple delay tasks concurrently, you may want to consider using asyncio
or threading
modules.
Basically that's it. If you want the for loop to run slower, just add time.sleep()
to it. It is not complicated but easy to ignore is to set the appropriate waiting time and usage scenarios.
The above is the detailed content of Python for loop with a delay or sleep. For more information, please follow other related articles on the PHP Chinese website!

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