# codes_9.py

import sys

from PyQt4 import QtGui, QtCore

class MySignal(QtCore.QObject):

# This class defines the new signal 'signal_writer'

signal_writer = QtCore.pyqtSignal()

class MyForm(QtGui.QWidget):

def __init__(self):

super().__init__()

self.initialize_GUI()

def initialize_GUI(self):

self.s = MySignal()

self.s.signal_writer.connect(self.write_label)

self.label1 = QtGui.QLabel('Label', self)

self.label1.move(20, 10)

self.resize(self.label1.sizeHint())

self.setGeometry(300, 300, 290, 150)

self.setWindowTitle('Signal Emitter')

self.show()

def mousePressEvent(self, event):

# This method handles when any of the mouse buttons is pressed. It is

# defined by default within the app. It can be overwritten according

# to how the event should be handled in each app.

self.s.signal_writer.emit()

def write_label(self):

self.label1.setText('Mouse was clicked')

self.label1.resize(self.label1.sizeHint())

def main():

app = QtGui.QApplication(sys.argv)

ex = MyForm()

sys.exit(app.exec_())

if __name__ == '__main__':

main()