pyqt qpushbutton icon

1import sys
2from PyQt4.QtCore import *
3from PyQt4.QtGui import *
4
5class Form(QDialog):
6   def __init__(self, parent=None):
7      super(Form, self).__init__(parent)
8		
9      layout = QVBoxLayout()
10      self.b1 = QPushButton("Button1")
11      self.b1.setCheckable(True)
12      self.b1.toggle()
13      self.b1.clicked.connect(lambda:self.whichbtn(self.b1))
14      self.b1.clicked.connect(self.btnstate)
15      layout.addWidget(self.b1)
16		
17      self.b2 = QPushButton()
18      self.b2.setIcon(QIcon(QPixmap("python.gif")))
19      self.b2.clicked.connect(lambda:self.whichbtn(self.b2))
20      layout.addWidget(self.b2)
21      self.setLayout(layout)
22      self.b3 = QPushButton("Disabled")
23      self.b3.setEnabled(False)
24      layout.addWidget(self.b3)
25		
26      self.b4 = QPushButton("&Default")
27      self.b4.setDefault(True)
28      self.b4.clicked.connect(lambda:self.whichbtn(self.b4))
29      layout.addWidget(self.b4)
30      
31      self.setWindowTitle("Button demo")
32
33   def btnstate(self):
34      if self.b1.isChecked():
35         print "button pressed"
36      else:
37         print "button released"
38			
39   def whichbtn(self,b):
40      print "clicked button is "+b.text()
41
42def main():
43   app = QApplication(sys.argv)
44   ex = Form()
45   ex.show()
46   sys.exit(app.exec_())
47	
48if __name__ == '__main__':
49   main()