Python PyQt program - Temperature converter

Python PyQt Widgets: Exercise-8 with Solution

Write a Python program that implements a temperature converter app that lets users choose between Celsius and Fahrenheit using PyQt. Customize the widget appearance based on the selected unit.

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.

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

QVBoxLayout Class: The QVBoxLayout class lines up widgets vertically.

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

QLineEdit Class: A line edit allows the user to enter and edit a single line of plain text with a useful collection of editing functions, including undo and redo, cut and paste, and drag and drop.

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.

QRadioButton: A QRadioButton is an option button that can be switched on (checked) or off (unchecked). Radio buttons typically present the user with a "one of many" choice. In a group of radio buttons, only one radio button at a time can be checked; if the user selects another button, the previously selected button is switched off.

Sample Solution:

Python Code:

import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QWidget, QVBoxLayout, QLabel, QLineEdit, QPushButton, QRadioButton
class TemperatureConverterApp(QMainWindow):
    def __init__(self):
        super().__init__()

        # Set the window properties (title and initial size)
        self.setWindowTitle("Temperature Converter")
        self.setGeometry(100, 100, 300, 200)  # (x, y, width, height)

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

        # Create radio buttons for unit selection
        self.celsius_radio = QRadioButton("Celsius")
        self.fahrenheit_radio = QRadioButton("Fahrenheit")

        # Create labels and input fields for temperature input and result
        input_label = QLabel("Enter Temperature:")
        self.input_field = QLineEdit()
        result_label = QLabel("Result:")
        self.result_field = QLineEdit()
        self.result_field.setReadOnly(True)

        # Create a convert button
        convert_button = QPushButton("Convert")
        convert_button.clicked.connect(self.convert_temperature)

        # Create layout for unit selection
        unit_layout = QVBoxLayout()
        unit_layout.addWidget(self.celsius_radio)
        unit_layout.addWidget(self.fahrenheit_radio)

        # Create layout for temperature input and result
        input_layout = QVBoxLayout()
        input_layout.addWidget(input_label)
        input_layout.addWidget(self.input_field)
        input_layout.addWidget(result_label)
        input_layout.addWidget(self.result_field)
        input_layout.addWidget(convert_button)

        # Create layout for central widget
        layout = QVBoxLayout()
        layout.addLayout(unit_layout)
        layout.addLayout(input_layout)

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

        # Set default unit to Celsius
        self.celsius_radio.setChecked(True)
        self.fahrenheit_radio.setChecked(False)

    def convert_temperature(self):
        try:
            temperature = float(self.input_field.text())
            if self.celsius_radio.isChecked():
                # Convert from Celsius to Fahrenheit
                converted_temperature = (temperature * 9/5) + 32
                self.result_field.setText(f"{converted_temperature} °F")
            else:
                # Convert from Fahrenheit to Celsius
                converted_temperature = (temperature - 32) * 5/9
                self.result_field.setText(f"{converted_temperature} °C")
        except ValueError:
            self.result_field.setText("Invalid input")

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

if __name__ == "__main__":
    main()

Explanation:

In the exercise above -

• Import the necessary modules.
• Create a "QMainWindow" named "TemperatureConverterApp" with a central widget.
• Set the window's title and initial size.
• Create radio buttons (celsius_radio and fahrenheit_radio) for selecting the temperature unit (Celsius or Fahrenheit).
• Create labels and input fields for temperature input (input_field) and display the result (result_field).
• Create a "Convert" button and connect its click event to the "convert_temperature()" method.
• Create layouts to arrange widgets, including unit selection and temperature input/result.
• The "convert_temperature()" method converts the input temperature between Celsius and Fahrenheit based on the selected unit and updates the result field accordingly.
• In the main function, we create the PyQt application, create an instance of the "TemperatureConverterApp" class, show the window, and run the application's event loop.

Output:

Flowchart:

Python Code Editor:

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