A Pressed
-----------

.. code-block:: python
    :caption: scripts/PYQT4/01_key_pressed/01_A_pressed/main.py:

    import sys
    from PyQt5.QtWidgets import QApplication, QMainWindow, QTextEdit
    from PyQt5.QtCore import Qt

    class CustomTextEdit(QTextEdit):
        def keyPressEvent(self, event):
            if event.key() == Qt.Key_A:
                self.append("You pressed the 'A' key!")
            else:
                super(CustomTextEdit, self).keyPressEvent(event)

    class KeyDetectionApp(QMainWindow):
        def __init__(self):
            super(KeyDetectionApp, self).__init__()

            self.text_edit = CustomTextEdit(self)
            self.setCentralWidget(self.text_edit)

            self.init_ui()

        def init_ui(self):
            self.setWindowTitle('Keyboard Event Detection')
            self.setGeometry(100, 100, 400, 300)

    if __name__ == '__main__':
        app = QApplication(sys.argv)
        window = KeyDetectionApp()
        window.show()
        sys.exit(app.exec_())


This example displays a message "You pressed the 'A' key!" in the text editor when the user presses the 'A' key.

- ``CustomTextEdit`` inherits from ``QTextEdit`` to add functionality for detecting user keyboard input.
  
- ``keyPressEvent`` is a function that detects and processes keyboard events. In this context, it detects the 'A' key input and outputs a message to the text editor.