Python chat application with PyQt - Messaging interface

Python PyQt Widgets: Exercise-11 with Solution

Write a Python program to build a chat application that displays messages after typing a new message. Use the PyQt module.

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

Sample Solution:

Python Code:

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

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

        # Set the window properties (title and initial size)
        self.setWindowTitle("Chat Application")
        self.setGeometry(100, 100, 400, 300)  # (x, y, width, height)

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

        # Create a QVBoxLayout to arrange the widgets
        layout = QVBoxLayout()

        # Create a QLabel widget to display chat messages
        self.chat_label = QLabel()
        self.chat_label.setWordWrap(True)  # Wrap long messages
        layout.addWidget(self.chat_label)

        # Create a QLineEdit for typing new messages
        self.message_input = QLineEdit()
        self.message_input.setPlaceholderText("Type your message here...and press Enter key.")
        self.message_input.returnPressed.connect(self.send_message)
        layout.addWidget(self.message_input)

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

        # Initialize chat history
        self.chat_history = []

    def send_message(self):
        # Get the message from the input field
        message = self.message_input.text()

        # Append the message to the chat history
        self.chat_history.append(message)

        # Update the chat display
        self.update_chat_display()

        # Clear the input field
        self.message_input.clear()

    def update_chat_display(self):
        # Display the chat history in the QLabel
        chat_text = "\n".join(self.chat_history)
        self.chat_label.setText(chat_text)

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

if __name__ == "__main__":
    main()

Explanation:

In the exercise above -

• Import the necessary modules.
• Create a "QMainWindow" named ChatApp with a central widget.
• Set the window's title and initial size.
• Create a QVBoxLayout named layout to arrange the QLabel for displaying chat messages and the QLineEdit for typing new messages.
• Create a QLabel widget (chat_label) to display chat messages and set setWordWrap(True) to wrap long messages.
• Create a QLineEdit widget (message_input) for typing new messages and connect its returnPressed signal to the send_message method.
• The "send_message()" method retrieves the message from the input field, appends it to the chat history list, updates the chat display, and clears the input field.
• The "update_chat_display()" method updates the QLabel with the chat history.
• In the main function, we create the PyQt application, create an instance of the ChatApp class, show the window, and run the application's event loop.

Output:

Flowchart:

Python Code Editor:

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