**Course Title:** PyQt6 Application Development **Section Title:** Working with Files and User Input **Topic:** Building an app that reads and writes files, with drag-and-drop and keyboard handling. (Lab topic) **Objective:** By the end of this lab, you will be able to build a PyQt6 application that reads and writes files, handles drag-and-drop events, and processes keyboard input. **Prerequisites:** Familiarity with PyQt6 basics, event-driven programming, and GUI components. **Lab Overview:** In this lab, we'll create a simple text editor application that allows users to open, read, and write text files. We'll also implement drag-and-drop functionality to make it easy for users to open files. Additionally, we'll handle keyboard events to provide shortcuts for common actions. **Step 1: Setting up the Project** Create a new PyQt6 project with the following structure: ```bash file_editor |____ main.py |____ ui | |____ file_editor.ui |____ resources | |____ icons |______init__.py ``` **Step 2: Designing the UI** Create a new UI file called `file_editor.ui` using Qt Designer. Design a simple UI with the following components: * `QTextEdit` widget to display the file content * `QPushButton` widgets for Open, Save, and Exit actions * `QLabel` widget to display the file path Save the UI file and generate the corresponding Python code using `pyuic6`. **Step 3: Implementing File I/O** Create a new class called `FileEditor` in `main.py` that inherits from `QWidget`. This class will handle file I/O operations. ```python import sys from PyQt6.QtWidgets import QApplication, QWidget, QTextEdit, QPushButton, QLabel, QFileDialog from PyQt6.QtGui import QIcon from PyQt6.QtCore import Qt class FileEditor(QWidget): def __init__(self): super().__init__() self.initUI() def initUI(self): self.setGeometry(300, 300, 800, 600) self.textEdit = QTextEdit() self.textEdit.setReadOnly(False) self.openBtn = QPushButton("Open") self.openBtn.clicked.connect(self.openFile) self.saveBtn = QPushButton("Save") self.saveBtn.clicked.connect(self.saveFile) self.exitBtn = QPushButton("Exit") self.exitBtn.clicked.connect(self.close) self.fileLabel = QLabel("No file selected") layout = QVBoxLayout() layout.addWidget(self.textEdit) layout.addWidget(self.openBtn) layout.addWidget(self.saveBtn) layout.addWidget(self.exitBtn) layout.addWidget(self.fileLabel) self.setLayout(layout) self.setWindowTitle("File Editor") self.show() def openFile(self): filePath, _ = QFileDialog.getOpenFileName(self, "Open File", "", "Text Files (*.txt)") if filePath: with open(filePath, "r") as file: self.textEdit.setText(file.read()) self.fileLabel.setText(filePath) def saveFile(self): filePath, _ = QFileDialog.getSaveFileName(self, "Save File", "", "Text Files (*.txt)") if filePath: with open(filePath, "w") as file: file.write(self.textEdit.toPlainText()) self.fileLabel.setText(filePath) ``` **Step 4: Implementing Drag-and-Drop** To enable drag-and-drop, we need to subclass `QWidget` and override the `dragEnterEvent`, `dragMoveEvent`, and `dropEvent` methods. We'll create a new class called `FileDropWidget` that inherits from `QWidget`. ```python import sys from PyQt6.QtWidgets import QApplication, QWidget from PyQt6.QtGui import QDropEvent, QDragEnterEvent, QDragMoveEvent from PyQt6.QtCore import Qt class FileDropWidget(QWidget): def __init__(self, fileEditor): super().__init__() self.fileEditor = fileEditor def dragEnterEvent(self, event): if event.mimeData().hasText(): event.accept() else: event.ignore() def dragMoveEvent(self, event): if event.mimeData().hasText(): event.accept() else: event.ignore() def dropEvent(self, event): if event.mimeData().hasText(): filePath = event.mimeData().text() self.fileEditor.fileLabel.setText(filePath) with open(filePath, "r") as file: self.fileEditor.textEdit.setText(file.read()) else: event.ignore() ``` **Step 5: Implementing Keyboard Handling** To handle keyboard events, we need to override the `keyPressEvent` method in our `FileEditor` class. ```python def keyPressEvent(self, event): if event.key() == Qt.Key.Key_Escape: self.close() elif event.key() == Qt.Key.Key_Open: self.openFile() elif event.key() == Qt.Key.Key_Save: self.saveFile() else: super().keyPressEvent(event) ``` **Putting it all Together** Now that we have implemented all the necessary components, let's create the main application. ```python def main(): app = QApplication(sys.argv) fileEditor = FileEditor() fileDropWidget = FileDropWidget(fileEditor) fileDropWidget.setGeometry(300, 300, 800, 600) fileDropWidget.show() sys.exit(app.exec()) if __name__ == "__main__": main() ``` **Running the Application** To run the application, save all the files and execute the `main.py` file using Python. **Example Use Cases** This application can be used as a simple text editor. You can open, read, and write text files. You can also drag-and-drop files to open them. **Resources** For more information on PyQt6, you can refer to the [official PyQt6 documentation](https://www.riverbankcomputing.com/static/Docs/PyQt6/). **Conclusion** In this lab, we've created a simple text editor application that allows users to open, read, and write text files. We've also implemented drag-and-drop functionality and keyboard handling. You can use this application as a starting point for your own projects. **Exercise** Try to add more features to the application, such as undo/redo functionality or syntax highlighting. **Leave a comment/ Ask for help** If you have any questions or need help, please leave a comment below.