PyQt5 Simple Interest Calculator.py

import sys
from PyQt5.QtWidgets import (QApplication, QDialog, QComboBox, QDoubleSpinBox, QVBoxLayout, QGridLayout, QLabel)


class AppDemo(QDialog):
	def __init__(self):
		super().__init__()

		principalLabel = QLabel('Principal:')

		self.principalSpinBox = QDoubleSpinBox()
		self.principalSpinBox.setRange(0, 100_000_000)
		self.principalSpinBox.setValue(1000)
		self.principalSpinBox.setPrefix('$')
		self.principalSpinBox.valueChanged.connect(self.calculate_interest)

		rateLabel = QLabel('Rate:')

		self.rateSpinBox = QDoubleSpinBox()
		self.rateSpinBox.setRange(0, 100) # 0% to 100%
		self.rateSpinBox.setValue(10) # 10% default value
		self.rateSpinBox.setSuffix('%')
		self.rateSpinBox.valueChanged.connect(self.calculate_interest)

		yearLabel = QLabel('Year:')

		self.yearsComboBox = QComboBox()
		self.yearsComboBox.addItem('1 year')
		self.yearsComboBox.addItems(
			['{0} years'.format(year) for year in range(2, 26)]
		)
		self.yearsComboBox.currentIndexChanged.connect(self.calculate_interest)

		amountLabel = QLabel('Amount:')
		self.dollarLabel = QLabel()

		girdLayout = QGridLayout()
		girdLayout.addWidget(principalLabel, 0, 0)
		girdLayout.addWidget(self.principalSpinBox, 0, 1)
		girdLayout.addWidget(rateLabel, 1, 0)
		girdLayout.addWidget(self.rateSpinBox, 1, 1)
		girdLayout.addWidget(yearLabel, 2, 0)
		girdLayout.addWidget(self.yearsComboBox, 2, 1)
		girdLayout.addWidget(amountLabel, 3, 0)
		girdLayout.addWidget(self.dollarLabel, 3, 1)

		vLayout = QVBoxLayout()
		vLayout.addLayout(girdLayout)
		self.setLayout(vLayout)

		self.calculate_interest()

	def calculate_interest(self):
		p = self.principalSpinBox.value()
		r = self.rateSpinBox.value()
		y = self.yearsComboBox.currentIndex() + 1
		amt = p * ((1 + (r / 100.0)) ** y)
		self.dollarLabel.setText('$ {0:.2f}'.format(amt))

if __name__ == '__main__':
	app = QApplication(sys.argv)

	demo = AppDemo()
	demo.show()

	sys.exit(app.exec_())