Asking for help, clarification, or responding to other answers. If you want to learn modern web development techniques with Python and Flask, you may find the second edition of my O'Reilly book useful: I'm a software engineer, photographer and filmmaker, currently living in Drogheda, Ireland. #16 Miguel Grinberg said Thansks very much ! Thanks!

2020-09-29T07:47:14Z. #1 Viktor said So if this event object can wait on any condition, how do we tell it when to end the wait? How should one take advantage of the "premove" function on chess.com? If some other part of the program calls exit_thread.set() at a time where the thread is doing some work inside the loop, then the thread will continue running, but as soon as it reaches the exit_thread.wait() call it will return True immediately and exit. What is the difference between a process and a thread? Can you please suggest? It can take up to 10 seconds from the time the exit_thread variable is set until the thread actually exits, and that is without counting the extra time that may pass until the thread reaches the sleep statement. Wait for You book. We've seen this clearly in the previous two sections. If you try this version of the wait, you are going to find that the script waits without overtasking the CPU, so you may think that we now have the perfect solution. If you need to wait for a subprocess to end, the subprocess package provides some functions to launch and wait for processes. In this case since that loop might waste 0.00000001% of the CPU and the OP is coding in C#, replacing this with something 'more efficient' would be a complete waste of time. Essentially, I have a flask template that I want to render, then wait of a serial port trigger. How do I substitute almond flour for all purpose flour? @Igor: I'm sorry but I don't understand your logic. I noticed in your full example of syncing on a result_available Event object, you explicitly declared result as a global in your background task method, but you didn't declare the result_available object as global. What's the point in using threads when you're processing in a linear fashion? wait-for-it is a script that will wait on the availability of one or more TCP services (i.e.

There is a counter option in previous answers, and I just applied it a bit differently. It uses a lot less CPU than the previous one, but we still have a CPU that is spinning. For that, the event object has a set() method. 2020-04-12T17:03:14Z, #22 Bennett Gould said 2019-02-13T20:50:57Z. Why are people protesting against supreme court nominee Amy Coney Barrett? 2020-03-06T10:24:22Z. We can sleep: Here is the entire script, in case you want to run it locally: The time.sleep() function will suspend the execution for the number of seconds passed in the argument. Here are the changes to the background thread to report progress percentages in a progress global variable: And now we can build a more intelligent wait that reports the percentage of completion every 5 seconds: This new while loop is going to wait for the result_available event for up to 5 seconds as an exit condition. By using our site, you acknowledge that you have read and understand our Cookie Policy, Privacy Policy, and our Terms of Service. I suggest you play with all the examples I provided to familiarize with these techniques and eventually use them to replace inefficient time.sleep() calls in your code! If you need to wait for a thread to finish, the pattern I presented in the previous section is what you should use. @bryan: reading a serial port is a waitable operation. But this isn't about that, it is about waiting. Sometimes we need to write a script in such a way that the script will run until a specific key is pressed or the particular script will execute based on the specific key or the program will wait for the specific amount of time until any key is pressed. How does an executor help if you need to wait for a file to appear on your disk, for example?

2019-02-06T19:51:27Z. That's all tkinter does. This is called busy waiting. Since the big sleep went for up to 300 seconds, now I'm going to do 100 sleeps of up to 3 seconds each. Setting the timeout value to 0 will disable the timeout: Multiple services can be tested by adding additional -s or --service options: By adding the -p or --parallel option, wait-for-it can do the same in parallel rather than serial: Status message output can be suppressed with the -q or --quiet option. But of course we want to report the result at the exact moment it is available. To report task progress during this time I'm going to replace the single sleep with a loop that runs 100 iterations sleeping a little bit in each, and this will give me the opportunity to report a progress percentage in each iteration.

How to prepare my party to reasonably be able to bring down a prismatic wall? 2019-02-05T23:33:41Z. __WNOTHREAD (since Linux 2.4) Do not wait for children of other threads in the same thread group. See this page by Jon Skeet about events and multi-threading. So the obvious improvement to the previous solution is to add something inside the while-loop that puts a brake to the CPU frantically evaluating the while-loop exit condition. What I'm going to do is take the code from the previous section and expand it to show a completion percentage while the wait is taking place. If you need to watch a directory for files and act on the files as they are dropped there or when existing files are modified, an event is not going to be useful because the condition that should set the event is external to the application. One thing to note is if you want to wait for multiple threads: WaitHandle.WaitAll() won't work by default, as it needs an MTA thread.

So I have two options here... and my entire program waits to the user's decision, ADD or PASS, #18 Miguel Grinberg said How would I use threading? @Pedro: I don't think you get the point of this article. Yes it works and sometimes is the best solution, but you want to avoid it if possible because it wastes CPU time. wait-for-it ¶. The operating system makes doing an efficient wait a lot easier! I came with a similar question (and knowledge level) to the original poster and this answer was very valuable to me - tasks are way more suitable for what I'm doing and if I hadn't found this answer I'd have written my own terrible thread pool. @Manuel: you need to show me the code that you are using, I can diagnose the problem without seeing the code. I hope this article motivates you to think more carefully about how you wait in your applications. The version of this function that you see above does not have the waiting part implemented, you can see a TODO comment in the place where the wait needs to take place. Let's say that we want our wait to be as efficient as possible. The check at 60 seconds would still return False because the background task still has one more second to go, so it will be the check at 75 seconds the causes the loop to exit. This was very helpful to me! host:port) before executing a user-defined command. Read 8,406 reviews from the world's largest community for readers.