Вычисление количества дней между датами с помощью компонента QCalendarWidget

Календарь PyQT

#!/usr/bin/python3
 
import sys
from PyQt4 import QtGui, QtCore
 
class Window_Calendar(QtGui.QWidget):
	def __init__(self,parent=None):
		QtGui.QWidget.__init__(self,parent)
		self.setGeometry(300,300,700,300)
		self.setWindowTitle("Calendar")
 
		self.cal = QtGui.QCalendarWidget(self)
		self.cal.setGridVisible(True)
		self.cal.move(20,20)
		self.connect(self.cal,QtCore.SIGNAL('selectionChanged()'),
						self.showDate)
 
		self.cal1 = QtGui.QCalendarWidget(self)
		self.cal1.setGridVisible(True)
		self.cal1.move(350,20)
		self.connect(self.cal1,QtCore.SIGNAL('selectionChanged()'),
						self.showDate)
 
		self.label = QtGui.QLabel(self)
		date = self.cal.selectedDate()
		self.label.setText(str(date.toPyDate()))
		self.label.move(130,230)
 
		self.label1 = QtGui.QLabel(self)
		date1 = self.cal1.selectedDate()
		self.label1.setText(str(date1.toPyDate()))
		self.label1.move(430,230)
 
 
		self.label2 = QtGui.QLabel(self)
		self.label2.setText(str(date.toPyDate()-date1.toPyDate()))
		self.label2.move(300,250)
 
	def showDate(self):
		date = self.cal.selectedDate()
		self.label.setText(str(date.toPyDate()))
		date1 = self.cal1.selectedDate()
		self.label1.setText(str(date1.toPyDate()))	
 
		a = date.toPyDate() # type: <class 'datetime.date'>
		b = date1.toPyDate()
		c = b - a
		c = str(c) 
		if c[0] == '-': c = c[1:] 
		c = c.split()[0] 
		self.label2.setText(c)	
 
app = QtGui.QApplication(sys.argv)
window = Window_Calendar()
window.show()
app.exec_()