Customizing widget behavior with PyQt event handling

Last update on April 25 2025 12:52:08 (UTC/GMT +8 hours)

Write a Python program that overrides a specific event handler to customize widget behavior using PyQt.

From doc.qt.io:

QApplication Class: The QApplication class manages the GUI application's control flow and main settings.

QWidget: The QWidget class is the base class of all user interface objects.

Qt module: PyQt5 is a set of Python bindings for the Qt application framework. It allows us to use Qt, a popular C++ framework, to create graphical user interfaces (GUIs) in Python.

Sample Solution:

Python Code:

import sys
from PyQt5.QtWidgets import QApplication, QWidget
from PyQt5.QtCore import Qt

class CustomWidget(QWidget):
    def __init__(self):
        super().__init__()

    def mousePressEvent(self, event):
        # Override the mousePressEvent to customize behavior
        if event.button() == Qt.LeftButton:
            print("Left mouse button clicked")
        elif event.button() == Qt.RightButton:
            print("Right mouse button clicked")

def main():
    app = QApplication(sys.argv)
    window = CustomWidget()
    window.setWindowTitle("Custom Widget Example")
    window.setGeometry(100, 100, 400, 300)
    window.show()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

Explanation:

In the exercise above -

Import the necessary modules.
Create a custom widget class "CustomWidget" that inherits from "QWidget".
Inside the CustomWidget class, we override the mousePressEvent event handler to customize its behavior. Depending on which mouse button was clicked (left or right), we print a message.
In the main function, we create a "QApplication", instantiate our custom widget (CustomWidget), set the window's title and geometry, and show the window.
When you run this program, it displays a window and start the application's event loop.
When you click the left or right mouse button inside the widget, it prints a corresponding message to the console.

Output:

Left mouse button clicked
Left mouse button clicked
Right mouse button clicked
Left mouse button clicked
Right mouse button clicked

Flowchart:

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