Python PyQt checkbox example

Python PyQt Connecting Signals to Slots: Exercise-13 with Solution

Write a Python program that creates a window with a checkbox, like a "yes" or "no" choice. When you click the checkbox to check or uncheck it, something should happen. Use the 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.

QCheckBox Class: The QCheckBox widget provides a checkbox with a text label.

QVBoxLayout Class: The QVBoxLayout class lines up widgets vertically.

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

Sample Solution:

Python Code:

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

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

        self.setWindowTitle("Checkbox Example")
        self.setGeometry(100, 100, 300, 100)  # (x, y, width, height)

        layout = QVBoxLayout()

        # Create a checkbox
        self.checkbox = QCheckBox("Check me", self)
        layout.addWidget(self.checkbox)

        # Create a label to display the checkbox state
        self.checkbox_state_label = QLabel("Checkbox state: Unchecked", self)
        layout.addWidget(self.checkbox_state_label)

        # Connect the checkbox's stateChanged signal to a slot that reacts to changes
        self.checkbox.stateChanged.connect(self.update_checkbox_state)

        self.setLayout(layout)

    def update_checkbox_state(self):
        # Check the state of the checkbox and update the label accordingly
        if self.checkbox.isChecked():
            self.checkbox_state_label.setText("Checkbox state: Checked")
        else:
            self.checkbox_state_label.setText("Checkbox state: Unchecked")

def main():
    app = QApplication(sys.argv)
    window = CheckBoxApp()
    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 "CheckBoxApp" that builds a window with a checkbox.
• Inside the window, there's a checkbox (self.checkbox) and a label (self.checkbox_state_label).
• Connect the checkbox's stateChanged signal to a slot function (self.update_checkbox_state) that reacts to changes in the checkbox's state.
• When you check or uncheck the checkbox, the label displays whether it's checked or unchecked.
• In the main function, we create the PyQt application, instantiate the "CheckBoxApp" class, and show the main window.

Output:

Flowchart:

Python Code Editor:

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