PyQt5 EventFilter cannot detect key press event

Question

I'm trying to get key input and filter in pyqt5 ui, but it's not detecting keypress, only getting 74 and 75 event.

class Ui(QMainWindow):
    def eventFilter(self, obj, event):
        # only returned 74 = 6 ? and 75 = 6 ?
        print("{} = {} ?".format(event.type(), QtCore.QEvent.KeyPress))
        if event.type() == QtCore.QEvent.KeyPress:
            print("key pressed!")
        return super(Ui, self).eventFilter(obj, event)

# main
if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = Ui(0.1)
    window.installEventFilter(window) # install filter
    app.exec_()