Pyqt qthread blocking gui. So its 100% normal and needed for event driven app.

Pyqt qthread blocking gui Mar 29, 2013 · Just no. Quoting from the QThread doc: “A QThread object manages one thread of control within the program. If you post the code in the vicinity of where you call app. deleteLater while it's still running is wrong and dangerous (and the main cause of your issue, because you're emitting finished in the thread); 3. work. The solution is to create 2 workers that live in different threads Hello, i wrote a small GUI to train different machine learning models. 2 Signals and slots across threads 4. 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. These functions were made public in Qt 5. 3, Qt-4. Matplotlib figures are actually handled as special Qt widgets by QtAgg. The number of rows is quite large. Dec 16, 2020 · Hi, I have an application with 2 threads. We’ll explore why GUI freezing occurs, how to use threading to offload tasks, and best practices for updating progress bars or busy indicators without blocking the interface. The solution is to move Connect and Listen to the run() method: Qt offers many classes and functions for working with threads. (may be 1800 ~ 3000 and each row has graph consisting of large data plot Jan 10, 2020 · Golden rule of Qt: You should not execute tasks that consume a lot of time in the main thread of the GUI since they block the event loop of Qt. Jan 11, 2025 · Luckily, you can get around this problem using PyQt's QThread class. What is the best (and hopefully simplest) way of preventing the application GUI from freezing up whenever a function like that is launched, and avoids the aforementioned issue? Jul 22, 2011 · I have a program which interfaces with a radio I am using via a gui I wrote in PyQt. run calls will run the requests in a thread, without blocking the Qt event loop, making the UI snappy and responsive. Feb 13, 2024 · For certain applications, you may find it useful to embed OpenCV in a PyQt interface. QThread::sleep () can be used in worker threads for simple pauses in background tasks, but consider more sophisticated synchronization primitives (QWaitCondition) for better control. exec_(), this loop is used to perform tasks such as checking events, signals, calling some functions, etc. Qt has QThread class to manage such threads (secondary threads) that perform long non-GUI tasks. since python is single threaded, any thread blocking inside of the GUI's thread will hang the application. N. Jan 9, 2017 · I can't use time. PyQt (via Qt) provides an straightforward interface to do exactly that. 2 QRunnable and QThreadPool 3. Therefore, instead of waiting from the GUI thread, start another thread that will create a semaphore to wait for the ssh sessions to close, and then have it call some callback from the GUI. Although qthread is typically a better approach to long running functions, calling app. I hope process run in backgorund . Using a QThread with QtInProcessKernelManager is a possibility but I'm not sure what method I should thread. QThread also provides static, platform independent sleep functions: sleep (), msleep (), and usleep () allow full second, millisecond, and microsecond resolution respectively. run() does not block the GUI. Conclusion And that’s it! I hope you’ll find the extended . Jun 21, 2018 · In your case the Listen() task is blocking and you call it in the constructor, and the QThread constructor runs in the GUI thread, that's why your GUI freezes. One for the main GUI and another used for heavy computations. QRunnable/QThreadPool Async-like Patterns in PyQt: Signals, Slots, and Beyond Step-by-Step Example: Building a Responsive Prime Checker App Best Practices for Async-like PyQt Apps References 1. MultiThreading The solution is simple: get your work out of the GUI thread (and into another thread). Does the GUI freeze for approx 10 seconds. I made one script some time ago to record the monitor frames of the user and now I am trying to create a GUI for it. Nov 13, 2025 · Integrating a Python console into a C++ GUI application unlocks powerful extensibility: users can script custom workflows, debug in real time, or interact dynamically with your app’s internals. PyQt is the Python bindings for Qt, providing a way to create GUI applications in Python, while harnessing the performance of an efficient C++ based framework. In PyQt6, multithreading can significantly improve the responsiveness and performance of your applications, especially when dealing with time-consuming operations. Jul 30, 2020 · Starting with Tk, later moving to wxWidgets and finally adopting PyQt. Its event loop doesn't block just because your QObject executes an infinite loop. Aug 26, 2021 · Resolution: I ended up using the QThread class and associated signals and slots to communicate between threads. Rather, do the calculations in the QThread, wait for the Thread to be finished and then open the Popup from your main gui thread. Dec 5, 2017 · I create a button and try to run multiprocessing when I click button , but the UI is become blocked . 04 freezes. So far I've tried the QThread, QSplashscreen and app. I'm hoping it can be useful as a goto-answer for similar questions so I spent a bit more time than usual preparing this. Nov 24, 2021 · A common problem when building Python GUI applications is “locking up” of the interface when attempting to perform long-running background tasks. Also, any blocking in the main thread does make the UI unresponsive, but events are still queued by the system: in fact, if a user event happens during a block that is short enough, it will be To leave the GUI responsive, the main class creates an object of the Saver class and a QThread to do the actual data saving (using moveToThread). If you do need to update the GUI from within the thread, Qt-4's queued connection signals make it easy to send data across threads and will automatically be invoked if you're using QThread; I'm not sure if they will be if you're using Python threads, although it's easy to add a parameter to connect(). So what probably makes the most sense in your situation would be to subclass QThread and make RunSecurityCheck a method of the QThread, and pass in your two text parameters to the constructor of the thread. B. sleep(), since both tell the system to temporarily suspend the thread. I wrote Code to test this. Sep 23, 2022 · If the pygame stuff is blocking/synchronous, you might run that alone in a thread and have it just emit signals which the main UI thread receives and deals with. Considering the above, you must execute the time-consuming task in another thread and send the information to the GUI thread through signals. The Python Global Interpreter Lock limits one thread to run at a time even if the machine contains multiple processors. Use PyQt's QRunnable and QThreadPool to build reusable QThread instances. Hello, I have a program that collects MODBUS serial data as a list in a QThread, and emits it to a PyQT5 GUI thread that processes the data then uses it to update GUI elements. In minimal examples, it works flawlessly, but once I add many GUI elements it becomes unstable, sometimes crashing in seconds or minutes, sometimes running fine for hours-- Pycharm shows no traceback, but with terminal Oct 11, 2016 · There are two main problems in your example: Firstly, you are emitting a signal to stop the worker, but since the signal is cross-thread, it will be posted in the receiver's event-queue. The problem is that my GUI slows way down where actions like mouse clicks aren't recognized until the validation function finishes. 12. Dec 18, 2023 · In the first post of this series on PyQt Using PyQt with QtAgg in Jupyterlab – I – a first simple example we have studied how to set up a PyQt application in a Jupyterlab notebook. So there's no way to safely create a QApplication (as opposed to a QCoreApplication) and/or a UI in another thread, You should create the QAppplication first, then use a single-shot timer to queue up the other application, before calling exec(). How can I fix it ? from PySide2 import QtCore,QtGui,QtWid Nov 8, 2015 · If you try the code in my answer, you will see that the code executed inside QThread. 1 Per-thread event loop 4. Jul 23, 2025 · Prerequisite: PyQt5 and multithreading Multithreading refers to concurrently executing multiple threads by rapidly switching the control of the CPU between threads (called context switching). What I do is spawn a worker Qthread from the GUI which is cpu heavy. Below if a working example. Jan 11, 2019 · QT application GUI on Ubuntu 16. The key to getting a seamless integration was to invoke the QtAgg -backend of Matplotlib. In this step-by-step tutorial, you’ll learn how to prevent freezing GUIs by offloading long-running tasks to worker QThreads in PyQt. To prevent this, you can use PyQt’s QThread class to run long-running operations in the background without blocking the main GUI thread. sleep() (and related) is fundamentally identical to time. Sep 30, 2022 · Qt does not support GUI operations of any kind outside the main thread. The focus is on two key components: Thread management using QThread and Python's threading module External process May 5, 2024 · Implementing background threads with QThread in PyQt allows you to perform time-consuming tasks without blocking the user interface. processEvents () you might get an alternative approach. Nov 19, 2020 · Starting with Tk, later moving to wxWidgets and finally adopting PyQt. We have used two smart cameras (ethernet). start() method of QThreadPool helpful in any of your PyQt/PySide GUI apps that have long-running tasks to be executed in the background. 1 What requires a running event loop? 2. That way your infinite Jul 30, 2021 · Basically, I am using pyqt5 for making a GUI application and am using threading for creating threads and lastly using queue I tried to send signals between main and child thread. One of the most effective ways to use `QThread` correctly is via the `moveToThread()` method—a pattern that separates Jun 16, 2022 · I am currently building a GUI using PySide6. Real Time Change of Widgets? was published in faq on November 19, 2020 (updated September 02, 2024) . 4 Feature comparison 4 Threads and QObjects 4. Building real applications, you'll find yourself wanting to perform long-running tasks. 6. Dec 1, 2021 · Try increasing the length of the delay now – for example, time. Use wait () to block the calling thread, until the other thread has finished execution (or until a specified time has passed). However, I cannot stop it. but without it. QueuedConnection or Qt. 2 Blocking the event loop 2. There is obviously some flickering whilst the list-widget is being updated, but I am able to select items, scroll up and down, click the button, etc. 1 QThread 3. Nov 17, 2025 · This blog will guide you through creating responsive progress indicators in PyQt. Obviously one of the main functions of the radio is to transmit data, but to do this continuously, I have to lo Aug 27, 2018 · 7 Answer: in your case I do not see the need to use QThread. GitHub Gist: instantly share code, notes, and snippets. And how does the Qt eventloop invoke the functions? Well, for Sep 15, 2022 · QThread already has a finished signal, you shouldn't overwrite it nor emit it on your own; 2. Oct 12, 2015 · 16 I'm in the process of writing my very first GUI application with PyQt4 and I've come upon a question that seems very basic, yet I don't seem to find a good answer: I'm using a thread to continuously perform a repeated task without blocking the main window. Jul 12, 2011 · I have a problem with keeping a GUI responsive using PyQt and Qthreads. In such cases, we would like to be able to perform these Use wait() to block the calling thread, until the other thread has finished execution (or until a specified time has passed). Employ the best practices for creating GUI apps with PyQt's thread support, and handle shared resources safely. Mar 26, 2025 · Streamline your PySide6 applications with efficient multithreading using QThreadPool. Job in Fort Leonard Wood - MO Missouri - USA, 65473. However, the worker is running a blocking while-loop, so pending events cannot be processed. Da Apr 12, 2019 · Re: "Blocking" a QThread until a signal has arrived Maybe there is an easier way: QIODevice, the base class of QProcess has a waitForReadyRead () function that can be used to blockingly wait for the readyRead () signal emit. Prerequisites: Installing Python OpenCV installation (pip install opencv-python) PySide or PyQt (pip install pyside6 Dec 21, 2023 · Using PyQt with QtAgg in Jupyterlab – I – a first simple example Using PyQt with QtAgg in Jupyterlab – II – excursion on threads, signals and events we saw that PyQt and its GUI-widgets work perfectly together with Matplotlib’s backend QtAgg. in your case sleep() is a blocking function that should not be used, Qt offers alternatives to it, and one of them is to use a QEventLoop with a QTimer: Jan 11, 2019 · QT application GUI on Ubuntu 16. In this step-by-step tutorial, you’ll learn how to prevent freezing GUIs by offloading long-running tasks to worker QThreads in PyQt. Aug 6, 2015 · Tutorial covering basics of PyQt Threading with real life example and step by step description of the code and methods used. In this tutorial, we’ll look at how to correctly integrate and manage a video captured by OpenCV in a PyQt application. You can see the gui here: When pressing the STOP button, I want add the ability closing everything before completion if necessary: Closing the gui window, shutting down the ongoing processes created by the Worker thread. - **PyQt Compatibility**: If your In this step-by-step tutorial, you’ll learn how to prevent freezing GUIs by offloading long-running tasks to worker QThreads in PyQt. load, the function you want to execute. While i would assume the GUI and the communication to be independent, the GUI is extremely unresponsive and seems to only update when messages are coming in. We are updating data (not images, only camera result data, very small) on MySQL server every 500ms. 8. May 20, 2014 · You shouldn't create a GUI in a separate QThread (you should see warnings when you do). Introduction In some applications it is often necessary to perform long-running tasks, such as computations or network operations, that cannot be broken up into smaller pieces and processed alongside normal application events. Oct 28, 2011 · Once the thread finished, the GUI unfreezes and everything is back to normal. Jan 13, 2020 · The problem is that with True while you are blocking the event loop of the secondary thread preventing the signals from being received, if you want to do a periodic task then use a QTimer. I guess it is a bit too much. 1 Introduction 1. : We use Pyside, but conversion to PyQt is quite straightforward. Jun 28, 2021 · I intend to have a GUI where one (later three) threads read live data from different sources with an adjustable interval (e. Furthermore, making the connection with Qt. Aug 14, 2017 · You should not update the GUI in another thread other than the main thread, you must use signals and slots to send the information from the secondary threads to the main thread. The training of the ML model works, the progress bar fills, but somehow it can't finish the function. Every interaction between your GUI and your Logic is being buffered by some non-blocking work around, and if you're like me, you'll have 3 or 4 different custom modules that keeps everything readable (but barely understandable). 3 Forcing event dispatching 3 Qt thread classes 3. For the GUI to refresh independently the communication part is in a QThread. In this chapter we will learn how to use PyQt to create a real-time spectrum analyzer that can be used with an SDR (or with a simulated signal). Jan 4, 2018 · Basic rule of Qt, you can only update the GUI from the main thread called GUI thread, check the following link so you understand the reason: doc. While Creating a GUI Jun 16, 2022 · I've inhereted a GUI code which is structured something like this: any button signal triggers a slot, those slots then call an external process to receive information and wait until that process fi May 6, 2021 · Based on examples online, created a worker QObject so the gui would not freeze while the long running loop continues. This works quite ok but I have one slot that makes my The TL;DR is I would like to hear from other people how they have implemented non-blocking operations (say, HTTP requests) within their FBS apps and if they have ever had any platform specific bugs with that / how they overcame it. Jan 14, 2020 · I'd like to have a non-blocking console, that contains the same namespace as my main process and can send signals to the main application. When a QObject is moved to a QThread it only tells the Qt eventloop that if it invokes a slot of that QObject it must be executed in the thread that manages the QThread (if the Qt::QueuedConnection or Qt::AutoConnection flag is used in the connection). The worker Qthread sends a signal containing a numerical Nov 2, 2024 · Multithreading is a powerful technique that allows you to perform multiple tasks concurrently within a single application. Otherwise we did not need to use any of Matplolib’s functionality. I have a method where I perform some heavy computation, that will end up freezing the GUI if left on the main thread. Apr 7, 2016 · I have a PyQT gui that has one gui thread, and 24 "tester threads. Jan 27, 2012 · For a simple chat program i use a c lib that is wrapped via boost::python. Previously, it had been purely CLI, but recently I've been trying to build a UI in PyQt, with great success but for one problem: thread blocking issues, nonresponsive GUI when actually calling the worker threads within my script. Thanks to the async / await syntax, we can keep the entire flow in the same function as before, including handling exceptions naturally. . I suspect Progress_dialog::progress_bar is being run on (and therefore blocking) the GUI thread. Dec 13, 2024 · By offloading long lasting processing or blocking calls to other threads we can keep the GUI thread or other time critical threads responsive. please try to make your examples more minimal (there was really no need for 3 windows) and Jun 21, 2017 · I have some problem adding rows at a qtableview using thread for preventing GUI blocking. I am running into some issues with the qthreadpool threading. The good way to do is to emit a signal from your thread and handle the message box part in your GUI thread. This project implements a graphical user interface (GUI) for serial port communication using PyQt5. 1) it does not block or freeze the GUI. Thread to QThread, to make it easier Jun 2, 2013 · I'm trying to learn how to use QThreads in a PyQt Gui application. There are a few ways to work around this, but probably the simplest is to simply call the worker's stop method May 18, 2015 · Hi, No, widget related stuff must happen in the GUI thread. I haven't really worked with threading, but I definitely suggest using slots/signals and a QThread to send a message back to the main GUI thread to update the GUI from there. However, this integration poses unique challenges: - **GUI Responsiveness**: Python scripts (especially long-running ones) can block the main thread, freezing the UI. " They work fine, but still seem to stay up when I close the gui. This article will guide you through the basics of multithreading in PyQt6, from simple thread usage to Dec 26, 2011 · I have a script I'm writing to batch download images from an imageboard via JSON/XML api. Jan 21, 2022 · Once the main gui is fully initialized, then the loading screen should disappear and the main GUI be displayed. It will simply freeze the whole program on startup (since it's called in the main window's __init__), as it completely blocks the event loop. assuming that what takes some amount of time is the delete/commit operations, it's those operation that must go in the thread while showing the progress dialog from the main thread, not the other way around. On my Linux system (using Python-3. Multi-Threading Do's and Don'ts was published in faq on July 30, 2020 (updated September 17, 2024) . QThread can either be instantiated directly or subclassed Sep 23, 2014 · I tried to make my PyQt4 program more responsive by moving some blocking code to a seperate QThread. 7 and PyQt-4. Nov 3, 2017 · On my Linux system (using Python-3. Each QThread instance represents and controls one thread. So just call whatever function you like in there (so long as it doesn't attempt to update the GUI). The validation thread calls a function in a separate python module that shouldn't know anything about PyQt since it is a general-purpose module that runs in both gui and non-gui applications. In this article, we will learn, how to use threading in Pyqt5. Aug 20, 2023 · Freezing or unresponsive graphical user interfaces (GUIs) are a common issue when performing time-consuming tasks in a PyQt application. For some reason, there is a specific part of my code right now that isn't working as May 27, 2025 · For introducing delays or performing time-based actions in the GUI thread, QTimer is the recommended and non-blocking solution. Dec 19, 2017 · The GUI implements a mainloop through app. In this tutorial, you'll learn how to create a PyQt multithreading application that uses QThreadPool and QRunnable classes. As it didn't work, I created this minimal example as a demonstration: import sys import time from Jan 3, 2022 · While loops are blocking. io/qt-5/thread-basics. What we are using - Intel Celeron dual core 1. However, `QThread` is often misunderstood, leading to common pitfalls like unresponsive UIs, race conditions, or crashes. Personal attempts with QThreads haven't been as successful though, so I can't really help. Nov 17, 2017 · You have to move the QTimer to the DataCaptureThread thread, in addition to that when the run method ends, the thread is eliminated so the timer is eliminated, so you must avoid running that function without blocking other tasks. Sep 15, 2014 · [SOLVED]Is there a problem with the following non-blocking sleep function? General and Desktop 5 Posts 3 Posters 7. html#gui-thread-and-worker-thread, also if you want to use a thread with some other Qt resource (not the GUI) it is advisable to use QThread, QThreadPoll and QRunnable. wait() is blocking for the calling thread, similarly to Python's join(). 2k Views 2 Watching Oldest to Newest Sep 11, 2023 · Note that QThread. Instead, just implement your infinite loop in a QObject subclass and then move that QObject to a thread with QObject::moveToThread (). so if we interrupt the loop we can get unexpected behavior like the one you observe. My goal is to achive something quite simple like this: Gui with a button, that Use wait() to block the calling thread, until the other thread has finished execution (or until a specified time has passed). He has written a number of popular Python books on the subject. Use QRunnable and QThreadPool to create reusable threads. AutoConnection is also required. The output of this code is pretty much what I would expect (i. PySide/PyQT non-blocking thread example. 10s) and plot these data in the main window. So its 100% normal and needed for event driven app. Jan 11, 2025 · Prevent GUI programmes from freezing by using PyQt's QThread, which you learnt how to do in this tutorial. qt. We The problem is how to stop (terminate|quit|exit) a QThread from the GUI when using the recommended method of NOT subclassing Qthread, but rather vreating a QObject and then moving it to a QThread. sleep(10) – and notice that it doesn’t affect the GUI anymore. 3 QtConcurrent 3. Perform long-running tasks without interrupting your UI. I have been looking for a way to handle this. 6GHz, RAM 2GB, 128gb SSD. A similar question has been asked by waszil in the comments here. We have used QNetworkmanager to grab images from the cameras. Nov 11, 2025 · It emits data from a worker thread every 10ms and updates a list-widget in the GUI. By subclassing QThread and overriding the run () method, you can define the work to be done in the background. Everything works fine. TL; DR; When do I need to use another thread in the context of a GUI? Only one thread should be used when some task can block the main thread called the GUI thread, and the blocking is caused because the task is time-consuming, preventing the GUI eventloop from doing its job normally. 1 Prerequisites 2 Events and the event loop 2. For now it has only a START and a STOP button, but the STOP button does not stop QThread is the thread "controller". Sep 23, 2016 · However, when I start executing a sequence from the programming widget the main window freezes and the photodetector readings stops with it while is executing the commands (I guess it keeps reading because is in another thread but it stops updating the main window's gui). I don't want to add the whole code here. Oct 15, 2020 · If a blocking function is called in the main Qt thread (no matter if the app is GUI driven or not), everything will be blocked and queued until that function returns, including any signal emission and consequent processing. This article will introduce PyQt's QThread and demonstrate two different methods to use it to prevent GUI freezing. Understanding the Problem: Main Thread Blocking In GUI applications, the main thread (or "event Feb 22, 2023 · These pages are all identical in content but disguise themselves as pyqt help pages. g. Nov 13, 2025 · Multithreading is critical for building responsive GUI applications, and PyQt (a Python binding for Qt) provides `QThread` to handle concurrent tasks. I am using PyQt5 and pyth Sep 17, 2020 · GUI elements (everything inherited or related to a QWidget subclass) must be created and accessed only from the main Qt thread. A simple GUI is written using PyQT. Aug 15, 2018 · 3 You do not use subprocess. processEvent () approaches, but the loading screen was frozen because the pyqt5 event handler isn't running. How can I gracefully close the threads to avoid python crashing Nov 15, 2020 · There is an incorrect conception of how threads, QThread, signals, etc. no gui. Sep 7, 2022 · 1 As stated in musicamante's comment routines run in a separate thread need to be independent of the GUI. 2) The thread indeed does terminate, but at the same time it freezes the entire application. e. Jan 27, 2012 · A simple GUI is written using PyQT. This solution also required fewer changes to my existing code to implement. Only one main thread can do any GUI updates. And finally, the icing on the cake: Nov 8, 2019 · Playing a sound appears to be a blocking operation, so GUI is unresponsive. Here is the important part. I need to wait for the thread to finish, but I can't use QThread::wait () because I must not block the main UI thread. Receiving messages is done via a blocking call to said lib. Feb 11, 2024 · By using a QtAsyncRunner instance and changing the slot to an async function, the runner. Following the advice here, I tried to use a QEventLoop. Popen() because it is blocking, and just one of the disadvantages of blocking tasks is that they do not allow the GUI to perform other jobs, for this Qt provides the QProcess class that does not block the event-loop: Sep 22, 2021 · (Parent is QApplication(0x1f5e760), parent's thread is QThread(0x1cc7df0), current thread is QThread(0x2267a10) QObject::setParent: Cannot set parent, new parent is in a different thread So my question is: can I create somehow widgets that have NO parent so I can whenever I want set to them a parent on a different thread? Jun 12, 2020 · Hi Its not blocking it its driving it. This guide offers practical steps for improving app performance by smoothly managing background processes, ensuring a responsive and dynamic user experience. I've been left with a lot of crashes in my attempts. But you dont have to use it. Unless of course you're implementing that infinite loop in a QThread subclass. A common problem when building Python GUI applications is the interface Aug 21, 2021 · How to run background tasks in a Python & Qt desktop application without freezing the window. To keep the GUI responsive i am using QThread. full german shepherd puppies for sale MCPA Instructor and Training - USMC LEP. Dec 21, 2020 · In the sections below, you’ll learn how to use PyQt’s built-in thread support to solve the issue of unresponsive or frozen GUIs and provide the best possible user experience in your applications. QThread: Low-Level API with Optional Event Loops QThread is the foundation of all thread control in Qt. Martin founded PythonGUIs to provide easy to follow GUI programming tutorials to the Python community. Aug 11, 2021 · "obj" lives in the same thread so when invoking the slots they will execute the same thread so the first function it executes will block the other. mostly pseudocode: import threading import queue Jun 17, 2021 · Note that the code shown doesn't appear to actually use the new thread created by the QThread instance. with moveToThread()), it will be executed in this QThread and not the calling one. Jan 8, 2017 · Since there are often questions about using QThread in PyQt, similar to yours, here is an example that shows how to correctly use threads in PyQt. I am trying to implement a display screen to Raspberry Pi that will dynamically 'live update' the result to represent the rate at which the data is being transmitted in a (data/sec format). calling thread. So, I'm trying to switch from threading. sleep in my pyqt application because that freezes the GUI thread, so the GUI will be completely frozen during this time. QThread is the central class in Qt to run code in a different thread Jul 21, 2011 · Non blocking Gui Qthread in qt3 By triperzonak in forum Newbie Replies: 2 Last Post: 13th September 2008, 15:06 Nov 17, 2025 · Table of Contents Understanding the Problem: Main Thread Blocking PyQt’s Threading Toolkit: QThread vs. QThread also provides static, platform independent sleep functions: sleep() , msleep() , and usleep() allow full second, millisecond, and microsecond resolution respectively. It allows users to connect to a serial port, configure various parameters, send data, and receive data in real-time. Once the Qt event-loop starts, the timer will immediately time-out and the PyQt5: Threading, Signals and Slots This example was ported from the PyQt4 version by Guðjón Guðjónsson. Jan 8, 2013 · Now I have a thread started, within it signals are connected from the gui to my object processing data but, when my application starts processing data, the main gui doesn't respond anymore. QThread. Thus I want to start a new thread, play sound, and delete the thread, all in a non-blocking manner. In your case, you don't have to do that. I have used qthreadpool for otber methods in my code, and it has worked just fine. I tried to use Oct 25, 2018 · I thought to understand, that when a slot is correctly defined with pyqtSlot and assigned to QThread (e. It makes all events go round and signal and slot works. Jul 23, 2025 · To address this issue, PyQt provides QThread, a class that allows developers to run code in separate threads, keeping the GUI responsive. 0. 3 DOs and DON'Ts 5 When should I use threads? 5 Apr 25, 2023 · On today storie, we will create a simple PyQt application, and display the feedback from the webcam using OpenCV library. To make your GUI respond quickly, you have 3 options: Use a different thread to access your database, OR Optimize your database-access code so that it is not time-consuming, OR Make your database-access code call QCoreApplication::processEvents () to process signals. Below are four different approaches that Qt programmers can use to implement multithreaded applications. I work on about developing a Qt GUI using Qt5 and PyQt. Jun 22, 2012 · Waiting for a thread to finish without blocking the main event loop The following code is called by a subclass of QThread in the cancel method. Jan 8, 2016 · 1 The function connected to the started signal will run the thread which it was connected, the main GUI thread. If you need heavy duty processing, you must use QThread, and communicate with the main app using signals (and only with them, as you can NEVER access, create and modify widgets from external threads). Jul 11, 2014 · I'm trying to write a short(one file pyqt) program which is responsive(so dependencies outside python/lxml/qt, especially ones I can't just stick in the file have some downsides for this use case b At this point your application has grown into something of a monstrosity. We have used QSocket for communicating with the Cameras (socket server). This is primarily because my program already uses Qt/PyQt4 for the GUI objects/widgets. I have stuff that runs for a while, with (usually) points where I could update a Gui, but I would like to split the main work out Apr 20, 2025 · Threading and Process Management Relevant source files This page documents PyQt's capabilities for managing threads and external processes, which are crucial for developing responsive applications that can perform background operations without freezing the user interface. Mar 5, 2016 · The main thread cannot refresh the database and update the GUI at the same time. Does your Python program need a Graphical User Interface (GUI)? With this learning path, you'll develop your Python GUI programming skills with PyQt. I can start the GUI and the Qthread and I can have the latter update the GUI. 31 I was researching for some time to find information how to do multithreaded program using PyQT, updating GUI to show the results. May 30, 2023 · Athletic Trainer, IT Trainer, Training Consultant, Training x video of blue film pyqt qthread blocking gui. processEvents () might be sufficient if called from the right place and could lead to a much simpler fix to your issue. May 14, 2016 · Waiting for QThread without interupting main thread How do you wait for a qthread to finish without blocking the main loop (thereby blocking the responsiveness of the main window)? I'm using PyQt5. hws tbcqcij qtlod ajkdd esfixbl rlz pnfq fnxwgv kvp lllinu wzugic vsinoa nmvl xuj pmsdqe