Hàm sleep trong Python
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While running a Python program, there might be times when you'd like to delay the execution of the program for some seconds. Show
The Python time module has a built-in function called With the sleep() function, you can get more creative in your Python projects because it lets you create delays that might go a long way in helping you bring in certain functionalities. In this article, you will learn how to use the Just note that delays created with Basic Syntax of time.sleep()To use After importing the Basic Example of time.sleep()In the code snippet below, I put a delay of 5 seconds between the 2 print statements, so the second print statement will run 5 seconds after the first print statement runs: You can also specify the delay in floating-point numbers: More Examples of time.sleep()You can get more creative with delays created by time.sleep() by combining it with You can also use time.sleep() to create multiple delays while looping through iterable data such as list or tuple. The example below shows how I did it with a list: The output: ConclusionThis article took you through how to use the
Keep coding! ADVERTISEMENT ADVERTISEMENT ADVERTISEMENT Web developer and technical writer focusing on frontend technologies. If you read this far, tweet to the author to show them you care. Tweet a thanks Learn to code for free. freeCodeCamp's open source curriculum has helped more than 40,000 people get jobs as developers. Get started Have you ever needed to make your Python program wait for something? Most of the time, you’d want your code to execute as quickly as possible. But there are times when letting your code sleep for a while is actually in your best interest. For example, you might use a Python In this tutorial, you’ll learn how to add Python
This article is intended for intermediate developers who are looking to grow their knowledge of Python. If that sounds like you, then let’s get started! Free Bonus: Get our free "The Power of Python Decorators" guide that shows you three advanced decorator patterns and techniques you can use to write to cleaner and more Pythonic programs. Adding a Python $ python3 -m timeit -n 3 "import time; time.sleep(3)" 3 loops, best of 5: 3 sec per loop 5 Call With $ python3 -m timeit -n 3 "import time; time.sleep(3)" 3 loops, best of 5: 3 sec per loop 8Python has built-in support for putting your program to sleep. The Here’s an example of how to use >>> If you run this code in your console, then you should experience a delay before you can enter a new statement in the REPL. Note: In Python 3.5, the core developers changed the behavior of You can test how long the sleep lasts by using Python’s Here, you run the The default number of times that Let’s create something a bit more realistic. A system administrator needs to know when one of their websites goes down. You want to be able to check the website’s status code regularly, but you can’t query the web server constantly or it will affect performance. One way to do this check is to use a Python Here you create If no errors occur, then your code prints out that all is well. Regardless of what happens, your program will sleep for 60 seconds. This means that you only access the website once every minute. The URL used in this example is bad, so it will output the following to your console once every minute: Go ahead and update the code to use a known good URL, like Adding a Python $ python3 -m timeit -n 3 "import time; time.sleep(3)" 3 loops, best of 5: 3 sec per loop 5 Call With DecoratorsThere are times when you need to retry a function that has failed. One popular use case for this is when you need to retry a file download because the server was busy. You usually won’t want to make a request to the server too often, so adding a Python Another use case that I’ve personally experienced is where I need to check the state of a user interface during an automated test. The user interface might load faster or slower than usual, depending on the computer I’m running the test on. This can change what’s on the screen at the moment my program is verifying something. In this case, I can tell the program to sleep for a moment and then recheck things a second or two later. This can mean the difference between a passing and failing test. You can use a decorator to add a Python Finally, the innermost function Now rewrite Here, you decorate One other change you’ve made is to add a Note: If you’d like to brush up on exception handling in Python, then check out Python Exceptions: An Introduction. There are a few improvements that you could make to your decorator. If it runs out of retries and still fails, then you could have it re-raise the last error. The decorator will also wait 3 seconds after the last failure, which might be something you don’t want to happen. Feel free to try these out as an exercise! Adding a Python $ python3 -m timeit -n 3 "import time; time.sleep(3)" 3 loops, best of 5: 3 sec per loop 5 Call With ThreadsThere are also times when you might want to add a Python Note: Threads are a method of doing concurrency in Python. You can run multiple threads at once to increase your application’s throughput. If you’re not familiar with threads in Python, then check out An Intro to Threading in Python. To prevent customers from noticing any kind of slowdown, each thread needs to run for a short period and then sleep. There are two ways to do this:
Let’s start by looking at Using $ python3 -m timeit -n 3 "import time; time.sleep(3)" 3 loops, best of 5: 3 sec per loop 8The Python shows a nice example that uses Here, you use Python’s Try running the code above in your terminal. You should see output similar to the following: As each thread runs and then sleeps, the logging output is printed to the console. Now that you’ve tried an example, you’ll be able to use these concepts in your own code. Using import logging import threading import time def worker(arg): while not arg["stop"]: logging.debug("worker thread checking in") time.sleep(1) def main(): logging.basicConfig( level=logging.DEBUG, format="%(relativeCreated)6d %(threadName)s %(message)s" ) info = {"stop": False} thread = threading.Thread(target=worker, args=(info,)) thread_two = threading.Thread(target=worker, args=(info,)) thread.start() thread_two.start() while True: try: logging.debug("Checking in from main thread") time.sleep(0.75) except KeyboardInterrupt: info["stop"] = True logging.debug('Stopping') break thread.join() thread_two.join() if __name__ == "__main__": main() 2The The reason you’d want to use Here’s how you add a Python In this example, you create Note: If you’d like to learn more about dictionaries, then check out Dictionaries in Python. Take a closer look at the code block above. How would you pass in a different sleep time to each worker thread? Can you figure it out? Feel free to tackle this exercise on your own! Adding a Python $ python3 -m timeit -n 3 "import time; time.sleep(3)" 3 loops, best of 5: 3 sec per loop 5 Call With Async IOAsynchronous capabilities were added to Python in the 3.4 release, and this feature set has been aggressively expanding ever since. Asynchronous programming is a type of parallel programming that allows you to run multiple tasks at once. When a task finishes, it will notify the main thread. Here’s an example from Python’s own documentation: In this example, you run Here’s a more compelling example from the Coroutines and Tasks portion of the In this code, you create a worker called When you run this code, your program will execute Now you’re using the concept of tasks, which you can make with Adding a Python $ python3 -m timeit -n 3 "import time; time.sleep(3)" 3 loops, best of 5: 3 sec per loop 5 Call With GUIsCommand-line applications aren’t the only place where you might need to add Python GUI code will run all its processing and drawing in a main thread called the event loop. If you use Fortunately, there are other methods you can use besides Sleeping in TkinterYou’ll start by looking at an example that uses Once you’ve run the code, press the button in your GUI. The button will stick down for three seconds as it waits for To get Here you create an application that is 400 pixels wide by 400 pixels tall. It has no widgets on it. All it will do is show a frame. Then, you call
In this case, your application will print a string to stdout after 3 seconds. You can think of You could use this functionality to improve user experience. By adding a Python Sleeping in wxPythonThere are two major differences between wxPython and Tkinter:
The wxPython framework is not included with Python, so you’ll need to install it yourself. If you’re not familiar with wxPython, then check out How to Build a Python GUI Application With wxPython. In wxPython, you can use Here, you subclass
When you run this code, you should see a small blank window appear without any widgets. After 4 seconds, you’ll see the string One of the benefits of using ConclusionWith this tutorial, you’ve gained a valuable new technique to add to your Python toolbox! You know how to add delays to pace your applications and prevent them from using up system resources. You can even use Python To recap, you’ve learned how to add Python
Now you can take what you’ve learned and start putting your code to sleep! Mark as Completed Watch Now This tutorial has a related video course created by the Real Python team. Watch it together with the written tutorial to deepen your understanding: Using sleep() to Code a Python Uptime Bot 🐍 Python Tricks 💌 Get a short & sweet Python Trick delivered to your inbox every couple of days. No spam ever. Unsubscribe any time. Curated by the Real Python team. Send Me Python Tricks » About Mike Driscoll Mike has been programming in Python for over a decade and loves writing about Python! » More about MikeEach tutorial at Real Python is created by a team of developers so that it meets our high quality standards. The team members who worked on this tutorial are: Aldren Geir Arne Jaya Jon Joanna Master Real-World Python Skills With Unlimited Access to Real Python Join us and get access to thousands of tutorials, hands-on video courses, and a community of expert Pythonistas: Level Up Your Python Skills » Master Real-World Python Skills Join us and get access to thousands of tutorials, hands-on video courses, and a community of expert Pythonistas: Level Up Your Python Skills » What Do You Think? Rate this article: Tweet Share Share EmailWhat’s your #1 takeaway or favorite thing you learned? How are you going to put your newfound skills to use? Leave a comment below and let us know. Commenting Tips: The most useful comments are those written with the goal of learning from or helping out other students. and get answers to common questions in our support portal. |
