Qeventloop example. processEvents (self, ProcessEventsFlags flags, int maximumTime) Process pending events that match flags for a maximum of maxTime milliseconds, or until there are no more events to process, whichever is shorter. If anyone's interested: Sep 28, 2022 · I need to be able to exclude a set of events from being processed by the event loop; I am aware there are flags that can be passed onto processEvents method (e. cpp qtbase v5. setRange (0, 99) progress. Here is example. Sep 16, 2018 · Once all the slots connected to signals triggered by events are executed, the control will eventually return back to the main event loop and the cycle begins anew. It is about understanding the event loop and WHEN tasks are scheduled and executed not WHY. By voting up you can indicate which examples are most useful and appropriate. qt. These are the top rated real world Python examples of PyQt4. The fact that one can "wait" on a QEventLoop without blocking the main thread suggests to me that the loop runs in a separate thread. Do not want to freeze the thread though while w Feb 6, 2014 · I'we started experimenting with unit testing in Qt and would like to hear comments on a scenario that involves unit testing signals and slots. io Apr 13, 2025 · Understanding when and how to utilize QEventLoop is crucial for writing more advanced and efficient Qt applications. You can rate examples to help us improve the quality of examples. It stores an OR combination of ProcessEventsFlag values. QEventLoop::ExcludeUserInputEvents, import asyncio import functools import sys import time # from PyQt6. C++ developers strive to build robust multithreaded applications, but multithreading was never an easy thing to do. connect - 2 examples found. I would be very much surprised if Qt is different in this respect. Programs that perform long operations can call either processOneEvent () or processEvents () with various ProcessEvent values OR'ed together to control which events should be delivered. I found out that problem is connected to QTcpSocket::waitForReadyR Nov 22, 2017 · I am using std::thread and QEventLoop extensively. Need to wait for the function to finish. QEventLoop ¶ class QEventLoop ¶ The QEventLoop class provides a means of entering and leaving an event loop. Python QEventLoop - 31 examples found. Here is an example of the code re-producing the problem. QtCore. [override virtual] bool Dec 29, 2016 · @ beecksche said in QEventLoop and QCoreApplication::processEvents: is there i difference Yes, a huge difference. From within the event loop, calling exit () will force exec () to return. In this article, Toptal Freelance Qt Developer Andrei Smirnov talks about several scenarios exploring concurrent programming with the Qt framework. These are the top rated real world Python examples of spyderlib. Even I tried some QEventLoop methods but couldn't manage to solve this problem. Contribute to sayfoo/Pyside6-examples development by creating an account on GitHub. show () await first_50 (progress) loop = asyncio. QEventLoop Class The QEventLoop class provides a means of entering and leaving an event loop. I made this trivial demo to learn how to deal with the QT loop in asyncio contex for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. QEventLoop(thread). The following are 6 code examples of quamash. It is irrelevant what they do when they get there. QEventLoop class provides a means of entering and leaving an event loop. What's reputation and how do I get it? Instead, you can save this post to reference later. QtWidgets import from PySide6. unexpected crashes also blinks ;) Sep 20, 2012 · for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. Thanks for any advice. Apr 18, 2021 · I am new to asyncio and I want to leverage it for my pyqt application to handle communication over a tcp connection. And you can't do qasync. The QCoreApplication class provides an event loop for Qt applications without UI. On the other hand Sep 20, 2012 · for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. And it works greatly. A common problem when building Python GUI applications is the interface QEventLoop::~QEventLoop () Destructs the QEventLoop object. Simply put: Want to run a function in another thread. Here is a code example. run_in_executor which is functionally identical to that of asyncio. py From MusicBox with MIT Detailed Description The QEventLoop class provides a means of entering and leaving an event loop. What you want to do afterwards depends on your application logic. It had suspend function to stop the timer, which is pretty neat. Jun 16, 2013 · I have an application in which I tried using a while loop but the application just hangs, and now I think I need to use QEventLoop to make the application work here is some of the relevant code def The PySide. It is necessary to call this function to start event handling. qGuiApp->exec() works, but it's not what I need. [virtual] QEventLoop:: ~QEventLoop () Destroys the event loop object. Jun 6, 2013 · Also I need to disallow user input. unexpected crashes also blinks ;) QEventLoop Class The QEventLoop class provides a means of entering and leaving an event loop. For one QEventLoop::exec is a "blocking" call, which means it will stop at that position and sleep until there are events to process. The ProcessEventsFlags type is a typedef for QFlags <ProcessEventsFlag>. You may also want to check out all available functions/classes of the module quamash , or try the search function . I have used QEventLoop to wait until QNetworkReply is finished. Here is an example: The code i would like to test is ( May 27, 2025 · Example of problem class MyThread : public QThread { protected: void run () override { // This loop runs forever, blocking the event loop // QThread::quit () will not stop this immediately. AllEvents) Enters the main event loop and waits until exit () is called. Upvoting indicates when questions and answers are useful. get_running_loop () with QThreadExecutor (1) as exec: await loop. run_in Learn to create a desktop app with Python and Qt. Sep 16, 2023 · At any time, you can create a QEventLoop object and call exec () on it to start a local event loop. Python QEventLoop - 42 examples found. QtCore , or try the search function . At any time, you can create a QEventLoop object and call exec () on it to start a local event loop. QEventLoop Qt introduction: At any time, you can create a QEventLoop object and call exec () on it to start a local event loop. Aug 6, 2013 · Each of them will create a QEventLoop object, and run it. More The following are 6 code examples of PyQt5. h. Hmm * goes off to ponder the This can be useful for example for running a job which uploads data to a network. for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. The QEventLoop class provides a means of entering and leaving an event loop. unexpected crashes also blinks ;) Dec 5, 2012 · Thanks for your example, dakron. Take QCoreApplication as an example, Sep 20, 2012 · for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. By default QThreadExecutor is used, but any class implementing the concurrent. 15. It just so happens that I stumbled upon a similar example right before I saw your post. The QEventLoopLocker operates on particular objects - either a QCoreApplication instance, a QEventLoop instance or a QThread instance. Aug 27, 2025 · If you need some CPU-intensive tasks to be executed in parallel, qasync also got that covered, providing QEventLoop. QEventLoop. Apr 26, 2013 · the program continues after QEventLoop::exec () returns (which happens when the timer fires and calls quit () on the event loop). See also processEvents (). unexpected crashes also blinks ;) for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. The best-known package for this is asyncio. [slot] void QEventLoop:: exit (int returnCode = 0) Tells the event loop to exit with a return code Sep 20, 2012 · for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. QEventLoop taken from open source projects. 9 on KDAB Codebrowser Sep 20, 2012 · for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. connect extracted from open source projects. Now, QThread automatically starts an event loop when its thread is started. This makes it possible to, for example, run a batch of jobs with an event loop and exit that event loop after the last job is finished. So to remedy to this issue, I use a thread with an infinite loop for each QProcess and it's seems to work, but I heard Async “Minimal” Example ¶ The Python language provides keywords for asynchronous operations, i. May 9, 2018 · Local QEventLoop - waiting for a signal from thread - prevent processing events from main event loop Asked 7 years ago Modified 7 years ago Viewed 2k times Jan 13, 2021 · In some examples I have seen has this pattern: QEventLoop instance => connect => exec (). You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example. unexpected crashes also blinks ;) Jul 23, 2014 · I have a Thread starting from my QMainWindow that has a busy loop (execute until MainWindow ask him to close) So far I am running this loop this way : @ /// Main Loop while (antThreadRunning) { QThread::msleep (150); }@ I was wondering if a QEventLoop would be more efficient For example: @ /// Main Loop, done in . Clearly I would not be using asyncio ONLY to print statements to the console. But sometimes there is a large amount of "payload" on the differents ouputs and some output datas seems to be lost. g. NET Microsoft Framework . May 23, 2025 · 1. Feb 22, 2008 · Re: QThread and QEventLoop - Idle Processing Thank you! That was exactly what I was looking for. unexpected crashes also blinks ;) Jun 26, 2023 · A QEventLoop (which is actually used by the QCoreApplication exec() itself) fundamentally works like the example above (nested loops included), but with some intricacies related to threading, object trees and event dispatching/handling, because there can be multiple levels of event loops and handlers. import logging import sys import datetime import asyncio import qasync from PyQt5. Member Function Documentation QEventLoop:: QEventLoop (QObject * parent = nullptr) Constructs an event loop object with the given parent. I found out that problem is connected to QTcpSocket::waitForReadyRead() which is buggy: Oct 3, 2024 · My sample code reproduces EXACTLY the behavior which my question is addressing. while (true) { // Do some long-running, CPU-bound work // No QEventLoop::exec () being called } } }; Cause 2: Long-Running Blocking Operations Even if you We would like to show you a description here but the site won’t allow us. See also awake (). \sa QEventLoop, QCoreApplication */ /*! Creates an event locker operating on the QCoreApplication. The function does some calculation in a loop and after that loop finishes it should wait for the timer to timeo Accueil Actualités IT Pro Conception Cycle de vie du logiciel Conception UML Merise Java Plateforme et langage Java Java Spring Dév. From within the event loop, calling exit() will force exec() to return. Jul 23, 2023 · Qt事件循环及QEventLoop的使用 Qt事件循环及QEventLoop的使用_kupeThinkPoem的博客-CSDN博客 六、QEventLoop类 QEventLoop即Qt中的事件循环类，主要接口如下： int exec (QEventLoop::ProcessEventsFlags flags = AllEvents) void exit (int returnCode = 0) bool isRunning () const. Be very careful when reentering the event loop "by other paths": it can lead to unwanted recursions! Let's go back to the Button example. int QEventLoop. unexpected crashes also blinks ;) We would like to show you a description here but the site won’t allow us. QEventLoop extracted from open source projects. 4w次，点赞51次，收藏278次。本文详细介绍了Qt中的事件循环工作原理，包括QCoreApplication主事件循环、事件传递、processEvents的用法、QEventLoop类以及如何实现嵌套和同步操作，涉及耗时任务调度和对话框处理等内容。 Jan 22, 2019 · Hello, I use several QProcess to start several daemons on Linux Os and "capture" there output in a slot when the signal readyRead () is emit by the QProcess. From that statement I can imagine MySocket is actually QTcpSocket and there is some connecting of slots going on that is not shown. At any time, you can create a QEventLoop object and call exec() on it to start a local event loop. QtCore import QObject, pyqtSlot, QThread for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. Sign up to watch this tag and see more personalized content for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. We enter a local QEventLoop, and when the reply has finished, the local event loop quits. While the code does someting else events may be queued up. Example #1 Source File: music. QEventLoop (). Details Sep 20, 2012 · for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. Whereas using a QEventLoop works to wait for the request, the problem is if there are other signals fired in other parts of the program they will execute first. exec_ (self, ProcessEventsFlags flags = QEventLoop. If we call QCoreApplication::processEvents () inside the doWork () slot, and the The ProcessEventsFlags type is a typedef for QFlags <ProcessEventsFlag>. The PySide. QEventLoop is designed for such cases. It is up to packages to implement an event loop, support for these keywords, and more. Executor interface will do the job. Python QEventLoop - 4 examples found. Jan 9, 2023 · Qt QFileSystemWatcher Example - Watch a directory and do some processing if it is changed with QEventLoop - qt_directory_watcher. This guide offers practical steps for improving app performance by managing background processes smoothly, ensuring a responsive and dynamic user experience. exec of QEventLoop QEventLoop loop; QObject::connect (thread, SIGNAL QNetworkReply doesn't offer a blocking API and requires an event loop to be running. Is connect able to understand that there is a local event loop and use it? QCoreApplication Class The QCoreApplication class provides an event loop for Qt applications without UI. Mar 28, 2018 · Before jumping main menu I must be sure that it's already updated. QEventLoop(app) would get the application's main event loop, not the thread's loop. PyQt. unexpected crashes also blinks ;) PySide6. These are the top rated real world Python examples of PySide2. by using the Python QEventLoop. QEventLoop. These are the top rated real world Python examples of PySide. You may also want to check out all available functions/classes of the module PyQt5. Web Développement Web et Webmarketing Développement Web AJAX Apache ASP CSS Flash / Flex JavaScript PHP Ruby Mar 4, 2017 · In about all event-driven GUI systems (including JavaScript in a browser, and the Windows API) the events do not happen asynchronously, but only when explicitly waited for by the code. Feb 14, 2025 · 3. I've searched a little and seen that QCoreApplication::processEvent process the loop for just once. Apr 29, 2016 · From my research, it seems that I should be able to install a QEventLoop on the new QThread I created, and then I can call processEvents() on that QEventLoop. QEventLoop 的典型使用场景 异步操作转同步：等待网络请求、数据库查询等异步操作完成。 自定义模态逻辑：实现非标准对话框或需要用户交互后继续执行的逻辑。 多线程事件处理：在非 GUI 线程中运行独立的事件循环。 定时等待：结合 QTimer 实现超时控制。 If you need some CPU-intensive tasks to be executed in parallel, qasync also got that covered, providing QEventLoop. , “async” to define coroutines or “await” to schedule asynchronous calls in the event loop (see PEP 492). Therefore the slider can only change position when the drawing is finished. NET C# VB. My application was working for several weeks and then it started to crash or freeze all the time. See full list on doc. QEventLoop allows the application programmer to have more control over event delivery. If flags are specified, only events of the types allowed by the flags will be processed. int QEventLoop::activateSocketNotifiers () Activates all pending socket notifiers and returns the number of socket notifiers that were activated. Can I do this using QTimer? The following are 6 code examples of . Returns the value that was passed to exit (). When you don't want to make your code complex (with a lot of signals/slots) and need a single flow with support of event-driven logic. Jul 19, 2022 · Hey this should be a pretty straightforward question. asyncio offers an API that allows for the asyncio @Marco As the slider changes, a function is called to draw on the screen. By the way, with QThread you could totally create the loop outside the thread and then just use moveToThread. Okay, that's the reason why the above code does not work. NET Windows Phone Windows Azure Dév. NET Microsoft DotNET Visual Studio ASP. Dec 19, 2021 · Is there any way to use QEventLoop as the main event loop in a QML application? NOTE: Yes, I do need to use QEventLoop as the main event loop. unexpected crashes also blinks ;) Sep 20, 2012 · In one minute I thought QEventLoop will help me out but then I hear it is not recommended. More Source code of qtbase/src/corelib/kernel/qeventloop. Feb 14, 2019 · 1 I'm trying to execute a network request and wait for the response before moving on. Aug 14, 2014 · I have made a class which queries data from the net. This function is especially useful if you have a long running operation and want to show its progress without allowing user input, i. I'm seeing a pattern in everyone's usage here -- pseudo-synchronous flow control, without blocking the main thread. cpp The QEventLoop class provides a means of entering and leaving an event loop. @ Reply to QEventLoop example on Fri, 21 Sep 2012 07:42:44 GMT In one minute I thought QEventLoop will help me out but then I hear it is not recommended. Let’s verify all this with a simple example. Basic Example The QEventLoop class provides a means of entering and leaving an event loop. Web Java Android Eclipse NetBeans . QtWidgets import QApplication, QProgressBar from qasync import QEventLoop, QThreadExecutor async def master (): progress = QProgressBar () progress. I've tried to make QEventLoop and exec it with QEventLoop::ExcludeUserInputEvents flag, but as documentation says it only delays an event handling: the events are not discarded; they will be delivered the next time processEvents() is called without the ExcludeUserInputEvents flag. See also QAbstractEventDispatcher Definition at line 55 of file qeventloop. Jun 15, 2021 · But how do I do it? To my understanding, qasync. futures. If you don't call setObjectName (), the name given to your thread will be the class name of the runtime type of your thread object (for example, "RenderThread" in the case of the Mandelbrot example, as that is the name of the QThread subclass). e. QEventLoop 的作用 事件循环：Qt 程序的主线程默认运行一个全局事件循环（通过 QApplication::exec() 启动），处理信号/槽、UI 事件、定时器等。 局部事件循环： QEventLoop 允许在某个代码块中临时启动一个独立的事件循环，直到调用 quit() 或外部条件触发退出。 Here are the examples of the python api qgis. Mar 26, 2025 · Streamline your PySide6 applications with efficient multithreading using QThreadPool. exit () will force exec () to return. Finally if there's a call to QEventLoop::quit (through a signal-slot connection) it will return control to the user code. Sep 20, 2012 · for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. That is accomplished by keeping a QEventLoopLocker with each job instance. However, I can't figure out how to do this. Sep 19, 2025 · 文章浏览阅读2. Jun 28, 2018 · I want my program to wait for the timeout of the QTimer to execute a specific method. void QEventLoop::aboutToBlock () [signal] This signal is emitted before the event loop calls a function that could block. More … Mar 21, 2022 · I have multiple QTimer in the same thread, in the slot connected to the QTimer, I use QEventLoop for synchronization, like http requests, but I found different QTimers may affect each other when th QEventLoop Classvoid QEventLoop::processEvents (QEventLoop::ProcessEventsFlags flags, int maxTime) Process pending events that match flags for a maximum of maxTime milliseconds, or until there are no more events to process, whichever is shorter. At any time, you can create a PySide. QEventLoop object and call exec () on it to start a local event loop. From within the event loop, calling PySide. More for example, creating a thread and using QEventLoop to block until thread finish; closing the application won't complete process and doesn't clear the process. Dec 3, 2020 · You'll need to complete a few actions and gain 15 reputation points before being able to upvote. 6rbvvbjc nfkhztk1 cjl ai 3rz2pk7 r5tgy cnvtg vg4f or2hth gmay0k