Python PyQt text display application

Last update on December 21 2024 07:44:37 (UTC/GMT +8 hours)

Write a Python program using PyQt5 that creates an application with a QPushButton and a QLabel. Whenever the button is clicked, the label's text should change.

Note:
The QPushButton widget provides a command button.
The QLabel widget provides a text or image display.

From doc.qt.io:

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

QMainWindow Class: The QMainWindow class provides a main application window.

QPushButton: The push button, or command button, is perhaps the most commonly used widget in any graphical user interface. Push (click) a button to command the computer to perform some action, or to answer a question. Typical buttons are OK, Apply, Cancel, Close, Yes, No and Help.

QLabel Class: The QLabel widget provides a text or image display.

QVBoxLayout Class: This class is used to construct vertical box layout objects.

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

Sample Solution:

Python Code:

import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QPushButton, QLabel, QVBoxLayout, QWidget

class TextChangeApp(QMainWindow):
    def __init__(self):
        super().__init__()

        # Set the window properties (title and initial size)
        self.setWindowTitle("Text Change Application")
        self.setGeometry(100, 100, 400, 200)  # (x, y, width, height)

        # Create a central widget for the main window
        central_widget = QWidget()
        self.setCentralWidget(central_widget)

        # Create a QLabel to display text
        self.label = QLabel("Python Exercises, click the button to get new exercises.")

        # Create a QPushButton
        self.button = QPushButton("Change Text")

        # Create a vertical layout
        layout = QVBoxLayout()

        # Add widgets to the layout
        layout.addWidget(self.label)
        layout.addWidget(self.button)

        # Set the layout for the central widget
        central_widget.setLayout(layout)

        # Connect the button click event to the change_text function
        self.button.clicked.connect(self.change_text)

    def change_text(self):
        # Change the text of the label when the button is clicked
        new_text = "Java Exercises!"
        self.label.setText(new_text)

def main():
    # Create a PyQt application
    app = QApplication(sys.argv)

    # Create an instance of the TextChangeApp class
    window = TextChangeApp()

    # Show the window
    window.show()

    # Run the application's event loop
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

Explanation:

In the exercise above -

• Import the necessary modules.
• Create a custom "TextChangeApp" class that inherits from "QMainWindow."
• Inside the class, create the window and widgets (QLabel and QPushButton) as well as set their properties and layout.
• Connect the button's click event to the change_text method, which changes the QLabel text when the button is clicked.
• In the main function, we create an instance of 'TextChangeApp', show the window, and start the application's event loop.

Output:

Flowchart:

Python Code Editor:

Previous: Creating a text display application with PyQt.
Next: Creating a custom widget with PyQt.