**Course Title:** PyQt6 Application Development **Section Title:** Multithreading and Asynchronous Programming **Topic:** Developing a multithreaded app that handles background tasks.(Lab topic) **Introduction** In this lab topic, we will explore how to develop a multithreaded application that handles background tasks using PyQt6. Multithreading is a crucial concept in application development, as it enables your application to perform multiple tasks concurrently, improving its overall responsiveness and performance. **Why Multithreading?** Before we dive into the lab, let's quickly discuss why multithreading is necessary. In a single-threaded application, the application's main thread is responsible for handling all tasks, including GUI updates, I/O operations, and computationally intensive tasks. This can lead to a sluggish and unresponsive application. Multithreading allows you to offload tasks that take a significant amount of time to a separate thread, freeing up the main thread to focus on GUI updates and other tasks that require immediate attention. **Lab: Developing a Multithreaded App** In this lab, we will create a simple application that uses multithreading to perform a time-consuming task – generating prime numbers within a given range. **Step 1: Create a new PyQt6 project** Create a new PyQt6 project using your preferred IDE or text editor. Name the project `prime_generator`. **Step 2: Create a Worker Thread** In this step, we will create a worker thread that will be responsible for generating prime numbers. Create a new file called `worker.py` and add the following code: ```python import threading from PyQt6.QtCore import pyqtSignal, QObject class PrimeWorker(QObject): finished = pyqtSignal(list) progress = pyqtSignal(int) def __init__(self, start, end): super().__init__() self.start = start self.end = end def run(self): primes = [] for num in range(self.start, self.end + 1): if self.is_prime(num): primes.append(num) self.progress.emit(num) self.finished.emit(primes) def is_prime(self, num): if num < 2: return False for i in range(2, int(num ** 0.5) + 1): if num % i == 0: return False return True ``` This worker thread uses the `QObject` class from PyQt6, which provides a convenient way to create threads that can communicate with the main thread using signals and slots. **Step 3: Create the Main Window** In this step, we will create the main window that will display the generated prime numbers. Create a new file called `mainwindow.py` and add the following code: ```python import sys from PyQt6.QtWidgets import QApplication, QWidget, QVBoxLayout, QPushButton, QListView from PyQt6.QtCore import QThreadPool from worker import PrimeWorker class MainWindow(QWidget): def __init__(self): super().__init__() self.initUI() def initUI(self): self.setWindowTitle("Prime Generator") self.setGeometry(100, 100, 400, 300) layout = QVBoxLayout() self.setLayout(layout) self.listView = QListView() layout.addWidget(self.listView) button = QPushButton("Generate Primes") button.clicked.connect(self.generate_primes) layout.addWidget(button) def generate_primes(self): worker = PrimeWorker(1, 1000) worker.finished.connect(self.display_primes) worker.progress.connect(self.update_progress) QThreadPool.globalInstance().start(worker) def display_primes(self, primes): self.listView.clear() for prime in primes: self.listView.addItem(str(prime)) def update_progress(self, num): print(f"Generating prime numbers... ({num})") def main(): app = QApplication(sys.argv) window = MainWindow() window.show() sys.exit(app.exec()) if __name__ == "__main__": main() ``` In this code, we create a main window with a button and a list view. When the button is clicked, it triggers the `generate_primes` method, which creates a worker thread and starts it using the `QThreadPool` class. **Step 4: Run the Application** Run the application by executing the `main.py` file. Click the "Generate Primes" button to start generating prime numbers. You will see the prime numbers being generated and displayed in the list view. **Conclusion** In this lab, we explored how to create a multithreaded application using PyQt6. We created a worker thread that generates prime numbers within a given range and displays them in a list view. This application demonstrates how multithreading can be used to offload computationally intensive tasks and improve the overall responsiveness of an application. **Practical Takeaways** * Multithreading is a powerful tool for improving application performance and responsiveness. * PyQt6 provides a convenient way to create threads that can communicate with the main thread using signals and slots. * The `QThreadPool` class provides a simple way to manage threads and schedule tasks. * Worker threads can be used to offload computationally intensive tasks and improve application performance. **External Links** * [PyQt6 documentation: QThreadPool](https://www.riverbankcomputing.com/static/Docs/PyQt6/api/python/QtCore/QThreadPool.html) * [PyQt6 documentation: QObject](https://www.riverbankcomputing.com/static/Docs/PyQt6/api/python/QtCore/QObject.html) **Leave a Comment/Ask for Help** If you have any questions or need help with this lab, please leave a comment below.