import sys
from PyQt4.QtCore import*
from PyQt4.QtGui import*
class ZeroSpinBox(QSpinBox):
    
    zeros = 0
    
    def __init__(self, parent=None):
        super(ZeroSpinBox, self).__init__(parent)
        
        self.connect(self, SIGNAL("valueChanged(int)"), self.checkzero)
    
    def checkzero(self):
        if self.value() == 0:
            self.zeros += 1
            self.nulls = 5
            self.emit(SIGNAL("atzero(int, int)"), self.zeros, self.nulls)
class Form(QDialog):
    
    def __init__(self, parent=None):
        super(Form, self).__init__(parent)
        
        dial = QDial()
        dial.setNotchesVisible(True)
        
        zerospinbox = ZeroSpinBox()
        
        layout = QHBoxLayout()
        layout.addWidget(dial)
        layout.addWidget(zerospinbox)
        self.setLayout(layout)
        
        self.connect(dial, SIGNAL("valueChanged(int)"), zerospinbox.setValue)
        self.connect(zerospinbox, SIGNAL("valueChanged(int)"), dial.setValue)
        self.connect(zerospinbox, SIGNAL("atzero(int, int)"), self.announce)
        
        self.setWindowTitle("Signals and Slots")
    
    def announce(self, zeros, nulls):
        print("ZeroSpinBox has been at zero %s times." % zeros)
        print("The constant nulls is %s" % nulls)
app = QApplication(sys.argv)
form = Form()
form.show()
app.exec_()