Python PyQt text updater application

Python PyQt Connecting Signals to Slots: Exercise-3 with Solution

Write a Python program that creates a one-line text editor where you can type text. Whenever you type something in that box, it should immediately show up somewhere else on the screen, like a label. Use PyQt module.

From doc.qt.io:

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

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

QLineEdit Class: The QLineEdit widget is a one-line text editor.

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

QVBoxLayout Class: The QVBoxLayout class lines up widgets vertically.

Sample Solution:

Python Code:

import sys
from PyQt5.QtWidgets import QApplication, QWidget, QLineEdit, QLabel, QVBoxLayout

class TextUpdaterApp(QWidget):
    def __init__(self):
        super().__init__()
        self.setWindowTitle("Text Updater App")
        self.setGeometry(100, 100, 400, 200)  # (x, y, width, height)

        layout = QVBoxLayout()

        # Create a QLineEdit widget
        self.line_edit = QLineEdit(self)
        layout.addWidget(self.line_edit)

        # Create a QLabel widget
        self.label = QLabel("Text Entered: ", self)
        layout.addWidget(self.label)

        # Connect the textChanged signal to the update_label slot
        self.line_edit.textChanged.connect(self.update_label)

        self.setLayout(layout)

    # Slot function to update the label text
    def update_label(self):
        text = self.line_edit.text()
        self.label.setText("Text Entered: " + text)

def main():
    app = QApplication(sys.argv)
    window = TextUpdaterApp()
    window.show()
    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

Explanation:

In the exercise above -

• Import the necessary modules from PyQt5.
• Create a custom "QWidget" class named "TextUpdaterApp" that inherits from QWidget.
• Inside the TextUpdaterApp class, we create a QLineEdit widget (self.line_edit) and a QLabel widget (self.label). Both widgets are added to a QVBoxLayout for layout management.
• Connect the textChanged signal of the "QLineEdit" to the update_label slot function using self.line_edit.textChanged.connect(self.update_label). This means that whenever the text in the line edit changes, the "update_label()" function will be called to update the label text.
• The "update_label()" slot function retrieves the text from the "QLineEdit" using self.line_edit.text() and updates the QLabel's text to display "Text Entered: " followed by the entered text.
• In the main function, we create the PyQt application, instantiate the TextUpdaterApp class, and show the main window.

Output:

Flowchart:

Python Code Editor:

Previous: Python PyQt button actions example.
Next: Python PyQt slider application.