import sysfrom PyQt4.QtCore import *from PyQt4.QtGui import *class Form(QDialog):        def __init__(self,parent=None):            super(Form,self).__init__(parent)                prinlabel=QLabel('Principal: ')        ratelabel=QLabel('Rate: ')        yearlabel=QLabel('Years: ')        amountlabel=QLabel('Amount: ')        self.numlabel=QLabel()                self.prinspinbox=QDoubleSpinBox()        self.ratespinbox=QDoubleSpinBox()        self.yearcombobox=QComboBox()                self.prinspinbox.setRange(1,10000000)        self.prinspinbox.setValue(1000)        self.prinspinbox.setPrefix("$ ")        self.ratespinbox.setRange(0.0001,1000)        self.ratespinbox.setValue(5)        self.ratespinbox.setSuffix(" %")                yearcon=[]        for i in range(60):            yearcon.append(str(i+1)+'  years')                self.yearcombobox.addItems(yearcon)                grid=QGridLayout()        grid.addWidget(prinlabel,0,0)        grid.addWidget(ratelabel,1,0)4        grid.addWidget(yearlabel,2,0)        grid.addWidget(amountlabel,3,0)                grid.addWidget(self.prinspinbox,0,1)        grid.addWidget(self.ratespinbox,1,1)        grid.addWidget(self.yearcombobox,2,1)        grid.addWidget(self.numlabel,3,1)                self.setLayout(grid)        self.setWindowTitle('Interest')                self.connect(self.prinspinbox,SIGNAL('valueChanged(double)'),self.updataUi)        self.connect(self.ratespinbox,SIGNAL('valueChanged(double)'),self.updataUi)        self.connect(self.yearcombobox,SIGNAL('currentIndexChanged(int)'),self.updataUi)            def updataUi(self):        principal=self.prinspinbox.value()        rate=self.ratespinbox.value()        years=self.yearcombobox.currentIndex()+1        amount=principal*((1+rate/100)**years)        self.numlabel.setText('$ %0.2f' % amount)        app=QApplication(sys.argv)form=Form()form.show()app.exec_()