How does the keyPressEvent method work in this program?

pyqt

Solution

e is the "event" that is generated when a user presses a key. This is pretty common in event handlers, it's a great way to pass information (such as which key got pressed - which is what's getting pulled with e.key()) to event handlers, so that we can combine related events and handle them with a single function.

# A key has been pressed!
def keyPressEvent(self, event):
    # Did the user press the Escape key?
    if event.key() == QtCore.Qt.Key_Escape: # QtCore.Qt.Key_Escape is a value that equates to what the operating system passes to python from the keyboard when the escape key is pressed.
        # Yes: Close the window
        self.close()
    # No:  Do nothing.

Problem

I'm having trouble understanding how the keyPressEvent method works in this program. Specifically, what is "e" here? Is keyPressEvent a redefined method using a pre-existing instance "e"? ``` import sys from PyQt4 import QtGui, QtCore class Example(QtGui.QWidget): def __init__(self): super(Example, self).__init__() self.initUI() def initUI(self): self.setGeometry(300,300,250,150) self.setWindowTitle('Event handler') self.show() def keyPressEvent(self, e): if e.key() == QtCore.Qt.Key_Escape: self.close() def main(): app = QtGui.QApplication(sys.argv) ex = Example() sys.exit(app.exec_()) if __name__ == '__main__': main() ```

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