Pyqt main loop.

Pyqt main loop May 28, 2024 · What is PyQt's QThread? QThread is a class in PyQt that allows developers to run code in parallel with the main thread, which handles the GUI. thread and by optionally suppressing potential warning issues. path actually uses some part of that main module. PyQt graphical user interface (GUI) applications have a main thread of execution that runs the event loop and GUI. getKey() to execute somewhere within the loop to handle keypad and also will need to do other background work. I've understood that using postEvent() would be useful since the event will be released as soon as the event-loop will begin. But, when the repeat condition is satisfied, even though the loop does iterate (prints 'test' again) - the ui and ui2 windows do not get displayed again, and subsequently the program hits the exit condition and 主循环（main loop）是Tkinter应用程序的核心。它是一个无限循环，用于监听用户输入并更新应用程序的界面。通过调用mainloop()方法，我们可以将主循环启动起来。 2. The signal part is there to provide a way to terminate the infinite loop - just do Ctrl+C (i. This is the function it freezes. PyQt를 사용해서 증권사 API를 이용한 자동 매매 프로그램을 작성하다보면 로그인이 완료될 때까지 다른 코드가 수행되지 않고 기다려야 하는 경우가 있습니다. argv)和sys. timer = QtCore. There is only one running event loop per application. Now, this is something that you should not typically do. So, here are some options: Do what the Tkinter docs recommend and use TkInter from the main thread. Nov 1, 2011 · Regardless there is no reason to manually create a second event loop. Jun 12, 2020 · In Qt, whether C++/Python/PyQt5/PySide2, you need to spin the main event loop via QApplication::exec() to have a proper running application. The code of the mainwindow maingui. Please visit https://discuss. 2546. After user clicks " Nov 5, 2015 · The exec() method "Enters the main event loop and waits until exit() is called" : the script will be blocked on the line app. An event loop is Oct 31, 2018 · 一、将两个类写入到一个Python文件夹中 使用Qtdesigner设计ui界面，实行界面分离，分别设计两个界面，一个是登录的界面，一个是主界面 然后新建一个Python文件，在文件中分别将这两个界面UI引入，分别创建两个类，一个是实现登录显示的类，另一个是实现主界面显示的类。 Jun 2, 2013 · Here is a working example of a separate worker thread which can send and receive signals to allow it to communicate with a GUI. close() does not just close the screen, it quits the program. When you connect to your lambda slot, the optional argument you assign idx to is being overwritten by the state of the button. The following programm should just count up and int and displays its value in a label. I would recommend having your settings dialog subclass QDialog rather than QWidget (it is a dialog, after all). First we'll create a series of simple windows on your desktop to ensure that PyQt is working and introduce some of the basic concepts. Jan 19, 2017 · I'll try to be much clear as possible. Updating these window-variables is possible, but not a good idea if extensive processing is needed. QMainWindow – show you how to create the main window that supports the menu bars, toolbars, and status bars. May 8, 2019 · QCoreApplication::exec: The event loop is already running I have looked at multiple similar questions on SO, but I cannot fix my problem. 0. Apr 15, 2017 · Secondly, processing events outside the main event loop (app. exit(main(sys. To review, open the file in an editor that reveals hidden Unicode characters. Q_ARG(str,"hello world")) Clunky, but it gets you there. Manager for handling shared data between them. Dec 23, 2022 · if the logic is more complicated you can use signals to communicate back to the main thread to do the GUI updates Updating GUI elements in MultiThreaded PyQT, but you must not update the GUI from a child thread. , creating, updating, or destroying widgets) are performed in the main thread of your application. Sep 30, 2022 · You can safely create an instance of QApplication outside your "main"-loop (as a different process) using multiprocessing, plus multiprocessing. Application events are generated primarily from users, but they can also be generated by other means, such as an Internet connection, a window manager, or a timer. When Button 'start' is pressed execute 'function' n-times until Button 'stop' is pressed (imagine a stopwatch) if I press Button 'start' again 'function' gets once again executed and so on. Please visit https://bugs. The main loop detects various events and sends them to the event object. This basic PyQt application is straightforward and easy to understand, making PyQt a great choice for beginners in GUI development. If you want to do repetitive operations, use QTimer, if you need to communicate with external sources (eg: network replies), use QThread or the appropriate 文章浏览阅读3. Like most frameworks, Qt has what is called called an event loop, which is usually run as soon as you call Q[*]Application. Obviously one of the main functions of the radio is to transmit data, but to do this continuously, I have to loop the writes, which causes the gui to hang. 수많은 위젯 중에서 여러분이 사용할 위젯을 선택하고 각 위젯 클래스의 사용법을 익혀야 합니다 . wait(); } If you want to let the main loop run while you're waiting. Not only does PyQt have a main loop that is set off by running QCoreApplication. Only upon receiving QThread::finished() would I close the window. For adding this button into the application, QPushButton class is used. QCoreApplication::exec: The event loop is already running. As a special case, modal widgets like QMessageBox can be used before calling exec(), because modal widgets use their own local event loop. I probably missing something obvious. qt. I have a very simple test script that control a Power Supply, the script measure some current from the Agilent Power Supply + Unit Under Test, then, the script Apr 9, 2013 · You could also do the polling in a different thread and send signals to the main thread. Unfortunately, due to licensing issues, Twisted doesn't come with a reactor for PyQt pre-packaged, and it should be obtained separately. clicked signal emits an argument that indicates the state of the button. The main event loop receives events from the window system and dispatches these to the application widgets. Mar 26, 2015 · So don't use a while loop. getKey() . switch_backend('agg') Dec 11, 2020 · PyQt is the product of the combination of the Python language and the Qt library. when it has entered its main event loop exec_(). A Qt application is composed of a main window, which contains a central widget, which in turn contains the main content of the application. e. With the support of a qt designer, we can build a GUI, and then we can get python code for that GUI. Nov 19, 2020 · Just to confirm, if I have to loop (other than based on time) in Qt, I guess I'll have to use the threading/process feature right? Martin Fitzpatrick. I made two simple buttons, one which starts a long calculation in a separate thread, and one which immediately terminates the calculation and resets the worker thread. Nov 18, 2018 · 測定して10秒休み、また同じ測定をする、というプログラムをPyQt5で作っています。 最初休むのにtime. _exec(), but it also hooks itself into the interpreter prompt's mainloop (and for that matter, pdb's main loop). In your case, you don't have to do that. exec_())注释掉，运行，发现还是不行，曾一度有手动敲代码实现界面的冲动… exit(): "Tells the thread's event loop to exit with a return code. No interaction, basically just want one button to start the process, and one button to kill it. During that time, the user won’t be able to interact with the application, resulting in a bad user experience. In a GUI application, the main thread is responsible for executing the program’s logic and managing the event loop. Hampus Nasstrom Oct 13, 2013 · This code is wrong because of the PyQt4 main loop. While while_loop() method is running the main dialog becomes irresponsible. Already have an account? Sign in to comment. reenter_qt, self. sleep() function but it still freezes. Dec 6, 2021 · I could run the threaded tkinkter without any issue if I didn't plot any new figure using matplotlib. QThread i subclass in QObject so your can connect just like QWidget old-style or new-style signal. Aug 1, 2014 · pyqt comes with its own (infinite) event loop so that you don't have to build your own. If your code depends on/responds to external state this can cause undefined behavior. path is a python module that you can import as standalone, but it knows what the main os module is, and each function of os. Does anyone know how to achieve this as simple as possible? I am new to Scrapy / PyQt / Multiprocessing / Twisted. Footer Aug 26, 2021 · Later, I create an instance of this widget in the main GUI thread. postEvent (self. and the window is also active, I can play with the window, Show me how your way, with no app. /main. 薏米薏米: import matplotlib matplotlib. io: QApplication Class: The QApplication class manages the GUI application's control flow and main settings. Example of QTimer usage: in main() before exec_(): Sep 7, 2012 · I have a PyQt4 class that displays a html form and fetches the input, thanks to previous questions here (an older one is here). Thus, for a combination of Jupyterlab (IPython), Python code and graphical (Py)Qt windows there are at least three blocking effects we must consider: Mar 20, 2022 · “Starting a Matplotlib GUI outside of the main thread will likely fail. timeout. entry ()) self. exec_()) would cause the script to end when the window is closed. That way Jan 8, 2016 · The function connected to the started signal will run the thread which it was connected, the main GUI thread. We will use it to get the python code from the Qt Creator. This is the reason why it blocks. I want the user to be able to process different images without closing and opening application for each image. Unless of course you're implementing that infinite loop in a QThread subclass. Sep 17, 2023 · 最后，解决"main thread is not in main loop"问题需要仔细分析代码，确保所有的线程和进程都正确地在主循环中运行，并且使用适当的同步机制来保证程序的正确性。 ### 回答3： 解决 "main thread is not in main loop" 的问题的方法取决于出现此错误的具体情况。 Events are handled by an event loop, also known as a main loop. You shouldn't even need to use the other Thread classes to do this, it's even bad to call GUI events from threads, it can lead to crashes. Your can find example in here , here and a lot of in google search result. QEventLoop(app)) exit(app. exec_()) - it stops in there forever and never gets to key_code = kp. The better we lay out our Widgets, the more polished and professional our GUI application can look. Sep 25, 2013 · When Python deletes the SettingsDialog object, PyQt will delete the underlying C++ object, and this is what causes the dialog to close again. 4Contact Dec 21, 2024 · Python PyQt Basic: Exercise-1 with Solution. pyplot afterwards. execute slots in response to signals raised, or raise signals which other Apr 18, 2018 · from test import s_main class Worker(QObject): finished = pyqtSignal() # give worker class a finished signal def __init__(self, parent=None): QObject. Feb 24, 2013 · I would like to have a non blocking ui, though I want to integrate the Twisted event loop in the PyQt main loop. KeyboardInterrupt), and it will stop immediately. 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. QApplication The QApplication class manages the control flow and major settings of GUI applications. Generally speaking, no user interaction can take place before calling . Then we'll take a brief look at the event loop and how it relates to GUI programming in Python. py : The labels show fine but each button runs "run3. This is just bare bone code of what I actually want to do, but it produces the same My question is somewhat related to Get a layout&#39;s widgets in PyQT but it's not a duplicate. 2 and Qt/PyQt 5. For the ISS-tracker window in the first video capture, threading is used to make a PyQt window work with “outside” variables. app. Sep 22, 2010 · I have an application that has a PyQT GUI. Overriding QThread::run() is the Java way to do multi-threading. exec_() alrea May 26, 2011 · The bigger problem was finding how to interface Twisted with PyQt. an Internet connection, a window manager, or a timer. Apr 18, 2015 · which I suppose is a fundamental for launching application in PyQt. mainloop()当然，如果不是root，则应使用Tk对象的名称代替root。方法2将线程设置为守护程序t = threading. It is important to remember that a QThread instance lives in the old thread that instantiated it, not in the new thread that calls run(). (knowing that no new events will be generated) For now, this what I've done: Dec 8, 2016 · @squirtgun I'm not sure why the link is not what you are looking for. I set up the GUI in the usual PyQT fashion: app = QtGui. Now I want to exit the main loop, do something else and restart the main loop with a different html form later. I created a function with a loop, with the X value being the number of butt Oct 14, 2021 · You cannot use time. Use QTcpSocket::readyRead() to be informed when you have received data on the socket. py主函数里 Dec 10, 2022 · It's not the window blocking, it's the application event loop, which is essential for almost any UI based toolkit to let it process user and system events (user input, window drawing, etc). Mar 1, 2016 · This tutorial was written on Ubuntu 14. Thread(target=your_func)t. pyplot as plt plt. exec_() starts the application’s main loop, waiting for user interaction. The more I read about multithreading, the more I got scared of it ("a million ways to do it wrong if you don't absolutely know everything about all of it" seems a common comment). call_soon (self. waiting with a signal from outside. invokeMethod(mywidget, "add_text", QtCore. ----- This is not a bug tracker. For example: import matplotlib. set_event_loop (self. Now I would like a program that does the following. The main thread and worker threads # Qt applications are event-based. signal(signal. The previous loop created a new widget for each drive in the loop. Update progress sleeps for 1 second and keeps looping. Just check an internal flag within the loop that is run within the thread. I am not able to update the progress value from the thread. Jun 25, 2019 · The issue I have is to make sure they are all started. Add the called slot (showTime). Possibly by moving your current main thread code into a worker thread. 12. 04 box with PyQt4, Python 2. execute slots in response to signals raised, or raise signals which other Feb 4, 2010 · Can I debug PyQt application when is main loop running ? Pdb, NetBeans, PyDev, all "freeze" when sys. exec_()) causes your application to branch off into handling code (e. (note: you can have multiple event loops per pyqt application, for instance threads can have an event loop (see below) and dialogs sometimes have their own event loops. I have some ideas for down the road, but this project is really just about teaching myself and not a 'needed product' so no worries on that (example for future would be using a few checkboxes to modify which items get printed out in the loop). RuntimeError: main thread is not in main loop. show() command makes the window visible, and app. The event handler deals with the event, then passes control back to the event loop to wait for more events. Or what can be problem, ple Feb 5, 2013 · I believe this is exactly what you're seeing: your Tkinter code in Thread-1 is trying to peek into the main thread to find the main loop, and it's not there. Jul 22, 2011 · I have a program which interfaces with a radio I am using via a gui I wrote in PyQt. PyQt supports all platforms including Windows, macOS and UNIX. Oct 22, 2017 · Allow me to elaborate a bit. Feel free to use any pre-existing signal that exists in the main thread, or define a new one inside a QObject that lives in the main thread. How can i fix that? I added time. I have a final button "Process" to process and save the image. show() sys. . Application can be closed from tray icon context menu. QCoreApplication. If you take a step back and think about what you want to happen in your application, then you can probably sum it up with "stuff to happen at the same time as other stuff happens". Use threads and processes. The main loop fetches events and sends them to the objects. An event loop manages all events of the PyQt application. exec() inside main(). The main loop is inside the QApplication::exec() , and that does not return till told to quit. – Pyqt / Pyside: thread-safe global queue + main loop integration (Python recipe) by Esteban Castro Borsani The main event loop receives events from the window system and dispatches these to the application widgets. KDE is an international community creating free and open source software. Feb 2, 2017 · All Qt GUI operations (including plotting) must be done in the main thread. show() right now and I have tried using . To achieve this we will employ the QThread class, that provides a cross-platform API to work with threads. 尝试方法1：使用multiprocessing（最后未使用） $ python . As @jsulm has said, if you want something to happen call from inside the main loop you need to use async calls on the serial port. Great, glad it did the trick! Just to confirm, if I have to loop (other than based on time) in Qt, I guess I’ll have to use the threading/process feature right? It depends on how long the loop While you can use these modules, PyQt provides a better way of doing it by using the QThread class and other classes. Only after you have closed all qt windows will anything remaining be executed. NB: using sys. I assume you want to run the scraper at regular intervals. Jan 21, 2015 · When you use PyQt/PySide in an interactive session, the event processing is set up automatically in the background in a way that allows you to interact directly with the objects. set_event_loop(qasync. Queue to pass tasks to the main thread: In that example, the thread will exit after the run function has returned. But after a while the GUI stops working, while the loop continous. Since both asyncio and PyQt use their own event loops, this would be impossible without qasync, which is created to solve this problem. argv) win = MainWindow() win. Thanks in advance. exec_() enters this loop, which is why you don't see the code following that execute. kde. to process events and avoid rendering the application unresponsible. You can acquire the data in a secondary thread, but you need to send it back to the GUI thread for plotting. – xioxox Sep 7, 2014 · Use QThread to create loop what your want. In most cases, this means keeping all GUI code within the main body of your script, and not inside functions or methods that are called from other threads. __init__(self, parent=parent) self. Calling update() several times normally results in just one paintEvent() call. Jun 2, 2011 · I would like to execute a method which can only be called once my QApplication is displayed, i. QTimer() timer. Final project goal: App Description. The script below will scrape all the urls once every 60 seconds. UR的出不克: 感谢，终于破案了. The event loop waits for an event to occur and then dispatches it to perform some task. If you are new to PyQt, I recommend this book. When the event loop stops running, exec_() returns, allowing sys. py and main. exec_() # run the PyQt main loop: Sign up for free to join this conversation on GitHub. 6w次，点赞42次，收藏66次。方法1最后写root. I am on a Xubuntu 12. exec_()) Jun 3, 2011 · So i would like my top-level QWidget to receive a signal as soon as the event-loop begins. Such an event loop Mar 23, 2018 · The QtCore. PyQt 从PyQt事件循环中执行Python代码 在本文中，我们将介绍如何在PyQt中执行Python代码，并将重点放在从PyQt事件循环中执行代码上。 PyQt是一个用于开发GUI应用程序的Python库，它提供了丰富的功能和灵活的界面设计选项。 Apr 7, 2021 · Inside your clock folder create an empty file named main. exec_()) is executed. Dec 18, 2023 · Such a “main event loop” for a graphical (PyQt) application started from your notebook competes with other loops as e. sleep(0. after(100, monitorInputsAndActionOutputs, root) return None # Don't worry about this bit it's not related to your GUI / loop if __name__ == '__main__': import sys sys. a looping function can re-emit itself to allow the GUI to update itself before calling this function again. You wrote everything practical. exec_()) to finally run, and this exits the program. Oct 18, 2023 · GUI applications are event-driven. However, as with any tool, there can be potential pitfalls. Generally speaking, no user interaction can take place before calling exec(). 7 and Scrapy 0. 后来才弄懂一个程序里只能有一个app，于是乎，我将PersonalInfo类里的app = QtWidgets. So for example you could create and show a window, and then add other widgets to it from within the python shell whilst the window is still visible. use('Agg') 加这个是有效的，但一定要加载代码的主函数里，否则仍然可能会报错。比如加载train. Jul 7, 2013 · Its event loop doesn't block just because your QObject executes an infinite loop. (E. Section 6. Typically, the more up-to-date the software, the easier the development should be. py and the function May 21, 2019 · In this tutorial we'll learn how to use PyQt to create desktop applications with Python. But I need key_code = kp. exec_() until the window is closed. exec(), and run the application's main loop until the user closes it: sys. initialize() win. Feb 2, 2010 · Just loop over the threads and call wait() for each one. However, a QThread's start() function executes its run() method in the thread after the thread is initialized so a subclass of QThread should be created and its run method should run LoadThread. next_guest_run_schedule) self. for triggered slots, or events) while within your loop. It's interesting that even after a Aug 25, 2021 · QPushButton is a simple button in PyQt, when clicked by a user some associated action gets performed. QMetaObject. setDaemon(True)t. Jun 9, 2015 · This function does not cause an immediate repaint; instead it schedules a paint event for processing when Qt returns to the main event loop. Since the progress bar value has to be updated while the gui is still running in its main event loop, I created a thread for it. Call the app. waiting==True: time. Oct 16, 2018 · And most GUI backends require being run from the main thread. Instead of looking for a high level strategic view of how to do it, I'm trying to understand what th Aug 21, 2023 · exec() starts an event loop just like you already do when calling app. exec_()) KeyboardInterrupt Whats happening here? Qt strongly builds on a concept called event loop. As far as I understood, one should use the join method to wait for the thread to be finished. mouse events. If you launch a long-running task in this thread, then your GUI will freeze until the task terminates. exit(app. for(int i = 0;i < 20;i++) { threadObj[i]. 10, with the examples developed and tested using Python 3. Example: A window having a Push Button, when clicked a message will appear "You clicked Push Button". py", line 13, in <module> sys. PyQt’s Layout Managers provide us with a productive way of arranging PyQt Widgets on a GUI. Jun 22, 2012 · As for my suggestion of using the main event loop instead of a local one, I remembered solving the exact same problem you have by reimplementing the closeEvent() method of the main window of the GUI to prevent if from closing, asking the thread to exit instead. Mar 27, 2023 · RuntimeError: main thread is not in main loop occurs when you try to update your Tkinter GUI from a different thread other than the main thread. I made this trivial demo to learn how to deal with the QT loop in asyncio contex Apr 15, 2015 · Then, i want to hide it and show the second MainWindow when the RFID Reader (who's working on "auto-reading mode") read an RFID Tag. start(1000) out of start. Understanding GUI Freezing Aug 9, 2020 · I want to update a progress bar in my main gui class from another module. When we call the application's exec_ method, the application enters the main loop. org for user support. Using PyQt we can create a minimal Qt application, containing just a single QPushButton as follows: Feb 28, 2019 · I've been trying to create an X number of buttons, based on the value of a variable in PyQt5, but my way is not working. Instead, just implement your infinite loop in a QObject subclass and then move that QObject to a thread with QObject::moveToThread(). exec()) causes your application to branch off into handling code (e. argv)) This is a super basic example of a air conditioning monitoring script with a GUI with a single button on it - maybe the button enables or disables the AC Oct 19, 2013 · I have a window/widget that shows after I press a button, is there a way to make the main window wait until the widget closes out? I am using . exec_() is to run the main loop, which must be called to start the event processing, and the method is called to enter the main loop of the program until the exit() is called. Nov 4, 2017 · separate-PyQt-event-loop-from-main-thread. PyQt is coming with the Qt Builder. Once execution gets to the line sys. processEvents() which means that the GUI will still accept e. qml called images; Creating a “Hello World” app. finished. connect(functions. refreshgui) timer. 要解决Tkinter RuntimeError主线程不在主循环中的错误，我们可以采取以下方法： Jun 22, 2015 · After executing start. qml, to hold our UI definition in QML; Create an empty folder alongside the main. argv) asyncio. start()_runtimeerror: main thread is not in main loop Oct 18, 2020 · The windows run normally when they are not contained within a loop, and they also run pretty well in the first iteration of the loop. sh" (the last in the loop) instead of the correct one. But your long_task function is blocking the event loop to process any event (including exiting) or be aware of its conclusion. run_forever @Slot def on_worker_done (self): """ When all our current asyncio tasks are finished, we must end the Jun 15, 2021 · I am developing an asynchronous PyQt application - meaning, I need both asyncio and PyQt. Jun 20, 2022 · Finally, we execute the application via app. When you call the exec() method, it starts an event loop and creates a thread that is referred to as the main thread. However, Qt handles the creation for you!) Apr 20, 2025 · The state is being changed from outside your event loop. Jan 25, 2024 · RuntimeError: main thread is not in main loop这个错误记录一下. ) You can use the signals & slots of the threads. But i am not sure yet as to how i should use that. Mar 26, 2025 · Processing events outside the main event loop (app. ) Sep 28, 2018 · I have a for loop in a QThread, which is started from the main GUI via a push button. Therefore, just switch to backends that do not use GUI: Agg, Cairo, PS, PDF, or SVG. exec_() runs an event loop until all the windows are closed. Jun 9, 2013 · I have a simple PyQt application, which has a tray icon and can be hidden from taskbar by clicking close button or tray icon. Thus, if you are running on an environment without GUI, it will throw RuntimeError: main thread is not in main loop. When we call the exec_() method of the application, the application enters the main loop. py named main. May 9, 2023 · The RuntimeError: Main Thread is not in Main Loop error is a common error message which is encountered by programmers who use GUI frameworks such as Tkinter, PyQt May 22, 2020 · The function of app. I couldn't gets my head around it. py in your editor and add the following skeleton code. 解决方法. That function is not running in a separate thread it is running on the main event loop and the main event loop waits to run until you exit that function. But if you do want it to wait, you can put it in a wait loop (whileself. def setupUI(self): . 3. The signal in the main thread is the clicked signal that comes with a QPushButton. 2. Although older versions may work for the most part, there may be some issues with missing methods, and bugs. self. Write a Python program to create a blank window using PyQt. 1)) and update the value of self. PyQt/PySide事件循环运行在哪里 在本文中，我们将介绍PyQt/PySide事件循环（event-loop）的工作原理以及它在哪些地方运行。PyQt和 Mar 12, 2014 · Pressing Ok button will run while_loop() method which prints some message on a screen. When the for loop is over I would like to come back to the main thread (which is inside the Gui class) and do something else. exec ()) Layout Managers. Visit our main page to know more: https://kde. instance() if app is None: app = QtWidgets. org to report bugs. continue_run = True # provide a bool run condition for the class def do_work(self): s_main() self. argv) However there is almost certainly a better way to lay out your gui. Aug 21, 2021 · Since Qt's main loop runs in our application's main thread, and our task runs in a secondary thread, the user interface remains active while the file is downloaded in the background. sleep in the pyqt main event loop as it would stop the GUI event loop from responding. Open up the main. They will be started sequentially in the event loop of _eventThread. ” 当时瞬间就感觉，事情不太对的样子。果然，他告诉我matplotlib只能运行在主线程里面： “set_wakeup_fd only works in main thread” 于是我，停止了思考（bushi . loops handling keyboard input for Juypterlab notebook cells. Events are generated mainly by the user of an application. py ^C^C^C^C^C^C^C^C Only when hitting the exit button in the application window, the application finally stops as we the expected KeyboardInterruptError: File ". I would have expected that the two event loops are disjoint and that when a signal is emitted in the main event loop the slot is called as soon as the main even loop processes that event regardless of the state of the QThread's event loop. An alternative is to use a QTimer to send a signal at regular intervals to do the polling. Below is the code: from Nov 1, 2020 · You can check if an event loop is already running with something like this: app = QtCore. While the interpreter prompt is spinning in circles waiting Dec 14, 2014 · PyQt 가 기본적으로 제공하는 위젯 (Widget) 클래스의 객체를 생성해서 만들 수 있습니다. I was wondering if I could emit some signal that would restart the main event loop after all the processes. As for the loop, I don't think you are showing the code that cause the problem. Apr 23, 2019 · exit is a static method of QCoreApplication and quit is a "static slot" (not sure what the difference is) of QCoreApplication. May 10, 2020 · Normally if your worker will be waiting a long time you should just stop and start a new worker later. For now i call the postEvent in the main function like so: Jul 23, 2023 · 当然，这不代表在执行子循环的时候，类似父循环中的界面响应会被中断，因为往往子循环中也会有父循环的大部分事件，执行QMessageBox::exec()，QEventLoop::exec()的时候，虽然这些exec()打断了main()中的QApplication::exec()，但是由于GUI界面的响应已经被包含到子循环中了 May 21, 2013 · If you think about it, the interpreter prompt is running a main loop waiting for your input. sleep(msec)を使ったら、GUIがフリーズすることがわかりました。 QT Apr 28, 2023 · Ensure that all Tkinter-related tasks (e. root. If your code depends on or responds to an external state, then this can cause undefined behavior. load, the function you want to execute. Here is how you use it: app = QApplication(sys. Use QMainWindow to create the main window for the PyQt application and call the show() method to display the window on the screen. exec() , you get the window to e. Mar 14, 2017 · When a signal calls a function you cannot stay in that function forever. PyQt：在GUI中运行循环 在本文中，我们将介绍如何在PyQt中运行一个循环。 PyQt是一个用于创建GUI（图形用户界面）应用程序的Python库，它基于Qt框架。 在GUI程序中经常需要使用循环来处理用户输入、更新界面等操作，但是如果循环阻塞了GUI线程，就会导致应用 It is called by Trio at the end of an event loop run in order to relinquish back to Qt's event loop. From the main GUI thread or any other thread (knock on wood) I can call: QtCore. From doc. The slot is a method in the worker function. QTcpSocket::readAll() into a buffer and strip out any complete lines (ending with "\n" perhaps) from the front of the buffer and insert the text info your QTextEdit. Apr 20, 2018 · I found out that my original question was actually two questions in one: in order to stop a secondary thread from the main one, you need two things: Be able to communicate from the main thread down to the secondary thread. Oct 20, 2021 · In the event loop, the queue is checked on each iteration and if a waiting event is found, the event and control is passed to the specific event handler for the event. exec(). Hello, I am currently starting to use PyQt5 and created my first GUI. QTimer class provides repetitive and single-shot timers. There will not be any event loop running in the thread unless you call exec(). py; Create a file alongside main. for triggered slots or events) while within your loop. By posting an event on the Qt event loop that contains Trio's next entry point, it ensures that Trio's event loop will be scheduled again by Qt. Eh, mostly yes. The hanging is coming from staying in this function. Oct 25, 2016 · Im making port scanner program with PyQt but Gui freezes when i activate loop. Allow user to enter n number of subreddit names into an line edit field, separated by a comma. ) asyncio. loop. emit() # emit the finished signal when the loop is Apr 15, 2017 · Secondly, processing events outside the main event loop (app. You can also unsafely do so, using threding. I can see in gui that there's extra space created. However, when I plot a new figure using pyplot, I'll get main thread is not in main loop for BooleanVar or any other tkinter var (StringVar, IntVar). org ----- This is not a technical support forum. Sep 3, 2023 · I've tried to avoid needing multithreading as long as possible but now I need something that is running while not blocking the main window. Since Twisted and a typical GUI library are both event-loop based, to make them work together we should use a custom reactor. The main loop of a PyQt scripts consists of the window methods, using the predefined window-variables. May 7, 2015 · The end effect was that the main thread event loop appeared serialized with the QThread event loop. An event loop is an infinite loop in which all events from the user, the window system, and any other sources are processed and dispatched. 上回说过了PyQt5环境的搭建，我们今天还简单的写几个小程序，对PyQt的编程熟悉一下，为下阶段的学习做个铺垫吧。 我记得初中学习计算机的时候，因为学习里面的机器都是windows98操作系统，使用的教材里面就画了最… app. GUI applications and main thread. from PyQt4 import QtGui,QtCore import sys Mar 6, 2016 · The QPushButton. Tkinter is not thread-safe, and it requires that all GUI updates be performed in the main thread. Plotting from a secondary thread is forbidden. @mrjj said in QEventLoop and QCoreApplication::processEvents: Well QEventLoop is a local event loop. 原始代码 Sep 7, 2023 · The window. That is why I wanted to be able to interact directly on the event loop to know how many pending event it has and when it will have processed all. Aug 28, 2020 · @Sherafati "An EVENT loop is a loop of EVENTS(signals)": not exactly. Dan. Calling any of them just tells the event loop of that thread to exit. There are two main approaches to running independent tasks within a PyQt application: Aug 6, 2015 · The design will be simple as that's not the main point of the post, and the backend will only use modules built into python (and PyQt of course) to reduce number of 3rd party dependencies required. Use queue. The main one will handle the thread stuff just fine. QApplication(sys. This article will explore how to use PyQt to create responsive and efficient GUI applications using multithreading. loop) self. We’ll develop a simple text editor program. Since it's till part of the main loop, other threads closing shouldn't affect it at all. In the "list of all members including inherited" for QApplication it includes exit (which obviously links to the QCoreApplication doc page), but doesn't include quit. Send the proper signal to stop the thread Pyqt / Pyside: thread-safe callbacks + main loop integration (Python recipe) by Justin Israel Forked from Recipe 578299 (A modified version that removes the seemingly unnecessary dispatching thread and queue, and replaces it with a simple function that wraps and posts the callback event. Sep 7, 2016 · What happens is that I call one function on the press of Button1 and I keep the event loop spinning inside the while loop by calling QCoreApplication. SIGINT, ) and also does some other things. I also have another loop for displaying the disk letters in those widgets. Feb 15, 2023 · You do not put a qDebug() into the main loop, you have put it after the main loop. py i get the message: "QCoreApplication:exec: The event loop is already running" I figured out, that it has something to do with the timer . This is the bare minimum For example, the os. 1. The QApplication. g. done = False # Set this explicitly as we might want to restart the guest run. But they can be generated by other means as well; e. create_task (self. As a special case, modal widgets like QMessageBox can be used before calling , because modal widgets use their own local event loop. Main Window, Menus, Toolbars, and Status Bars # This section shows you how to create the main window and other commonly used widgets like menu bars, toolbars, and status bars. """ QApplication. Thanks. py This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. A solution in pyqt could look like this, using QTimer. I'm new to Qt4 (using PyQt4): i was hoping to have a on_start() -like callback, but didn't find one. I think it's because they all have the same name but how can I create launcher1, launcher2, etc in a loop? People say to use dictionaries instead of creating dynamic variable names but I don't understand how that would work. 4. Jan 3, 2023 · RuntimeError: main thread is not in main loop. It's a loop that waits for any event (usually user events, but also timed or system events), and, after processing the first available event, it starts again (hence, loop) waiting for more events in the queue; if there are more queued events waiting, they will be processed (usually in their insertion order), otherwise it Dec 29, 2016 · On the other hand QCoreApplication::processEvents() will process as many events there are in the event loop at the time of call and return control to the user code immediately (on first possible occasion). Before we dive into the different Qt widgets, let’s look at the layout of a typical Qt application. so in the main python program i have a pseudo "do while" loop (while True: and break with a condition) to read on serial port the data provided by the reader. This permits Qt to optimize for more speed and less flicker than a call to repaint() does. By moving time-consuming operations to a QThread, the main thread remains free to handle user interactions and updates, preventing the application from freezing. exec() to start the event loop. exec_()) The problem is that right after this I have a while loop that handles signals (signal. ". It checks the event queue continuously and forwards the events to their handlers. hsphai lxuw esbn bzweakxu gdpdza gtjs unedsi zlfvkvcuz vymv cfau xdbzoif vigvrt rdi bdhtsrg bdrfah