title: PyQt: How can I quit a QDialog?
body: <p>I've build a QDialog Widget. My problem is, I can't quit the QDialog. 
  If I press one of the buttons, then the QDialog is only set to "hide".
  Here is a little part of the code. It is executable. 
  I don't know what I'm doing wrong. Maybe one of you can tell me.   </p>
  
  <pre><code>from PyQt4.QtCore import *
  from PyQt4.QtGui import *
  import sys
  
  class MyClass(QDialog):
      def __init__(self, parent=None):
          QWidget.__init__(self, parent)
  
          # init
          # ------------------------------------------------
          self.setMinimumWidth(600)
          self.setWindowTitle("Select Dingsda")
          self.layout = QVBoxLayout()
          self.setLayout(self.layout)
          self.layoutWidget = QWidget(self)
          self.liste = []
          # widgets and layouts
          # ------------------------------------------------
  
          tempLayout = QHBoxLayout()
          self.cancelButton = QPushButton("Cancel")
          self.connect(self.cancelButton, SIGNAL('clicked()'), self.cancel)
          self.addSelectedButton = QPushButton("Add Selected")
          self.connect(self.addSelectedButton, SIGNAL('clicked()'), self.addSelected)
          tempLayout.addStretch()
          tempLayout.addWidget(self.cancelButton)
          tempLayout.addWidget(self.addSelectedButton)
          self.layout.addLayout(tempLayout)
  
          # test-data
          # ------------------------------------------------
      # methods
      # ------------------------------------------------
  
      def cancel(self):
          self.close()
  
      def addSelected(self):
          self.liste = ["1", "2", "3", "4", "5"]
          self.accept()
  
  
      def exec_(self):
          if QDialog.exec_(self) == QDialog.Accepted:
              return  self.liste
          else:
              return []
  
  def test():    
      app = QApplication([""])
      form = MyClass()
      i = form.exec_()
      print i
      sys.exit(app.exec_())
  #-------------------------------------------------------------------------------
  # main
  #-------------------------------------------------------------------------------
  if __name__ == "__main__":
      test()
  </code></pre>