Python PyQt comboBox example

Python PyQt Connecting Signals to Slots: Exercise-5 with Solution

Write a Python program that creates a combo box with different items. When you select an item from the list, it should appear somewhere on the screen immediately. 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.

QComboBox Class: The QComboBox widget is a combined button and popup list.

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, QComboBox, QLabel, QVBoxLayout

def main():
    app = QApplication(sys.argv)
    window = QWidget()
    window.setWindowTitle("Combo Box Example")
    window.setGeometry(100, 100, 400, 200)  # (x, y, width, height)

    layout = QVBoxLayout()

    # Create a QComboBox widget
    combo_box = QComboBox(window)
    combo_box.addItem("Python")
    combo_box.addItem("Java")
    combo_box.addItem("C++")
    layout.addWidget(combo_box)

    # Create a QLabel to display the selected item
    label = QLabel("Selected Item: ", window)
    layout.addWidget(label)

    # Connect the combo box's currentIndexChanged signal to update_label slot
    def update_label():
        selected_item = combo_box.currentText()
        label.setText("Selected Item: " + selected_item)

    combo_box.currentIndexChanged.connect(update_label)

    window.setLayout(layout)
    window.show()

    sys.exit(app.exec_())

if __name__ == "__main__":
    main()

Explanation:

In the exercise above -

• Import the necessary modules from PyQt5.
• Create a PyQt application and a main window.
• Create a "QComboBox" widget called combo_box and add three items to it.
• Create a "QLabel" widget called label to display the selected item.
• Define a slot function called "update_label()" that updates the label text with the currently selected item from the combo box.
• Connect the "currentIndexChanged" signal of the combo box to the "update_label()" slot function, so that the label is updated whenever the selection changes.
• At last, we display the PyQt application's main window and start its event loop.

Output:

Flowchart:

Python Code Editor:

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