[PyQt] cannot emit destroyed event

[机械唯物主义 : linjunhalida]

here is my code, and after close the window,
stop method is not triggered as expected. what's wrong?
windows + pyqt4.5.4

from PyQt4.QtCore import *
from PyQt4.QtGui import *

class MyClass(QWidget):
   def __init__(self):
       QWidget.__init__(self)
       self.destroyed.connect(self.stop)

   def stop(self, e=None):
       print("stoped")

def main():
   app = QApplication([])
   c = MyClass()
   c.show()
   app.exec_()

if __name__=="__main__":
   main()
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