In this article, we will see how we can create a loan calculator using PyQt5, below is an image that shows how is the loan calculator will look like :
PyQt5 is cross-platform GUI toolkit, a set of python bindings for Qt v5. One can develop an interactive desktop application with so much ease because of the tools and simplicity provided by this library
GUI implementation steps :
1. Create a heading label that display the calculator name
2. Create label and line edit pair for interest rate, label to show what user has to enter and line edit to enter text
3. Similarly create a pair for number of year and for amount
4. Create a push button to calculate
5. Create a label to show the calculated monthly payment
6. Create a label to show the calculated total amount
Back end implementation steps :
1. Make the line edit to accept only the number as input
2. Add action to the push button
3. Inside the push button action get the text of the line edits
4. Check if the line edit text is empty or zero then return so that function will not execute further
5. Convert the text value into integer
6. Calculate the monthly amount and set this value to the label
7. Calculate total amount from the monthly amount and show this value through label
Below is the implementation :
Python3
# importing required librariesfrom PyQt5.QtWidgets import *from PyQt5 import QtCore, QtGuifrom PyQt5.QtGui import *from PyQt5.QtCore import *import sysclass Window(QMainWindow): # constructor def __init__(self): super().__init__() # setting title self.setWindowTitle("Python ") # width of window self.w_width = 400 # height of window self.w_height = 500 # setting geometry self.setGeometry(100, 100, self.w_width, self.w_height) # calling method self.UiComponents() # showing all the widgets self.show() # method for adding components def UiComponents(self): # creating head label head = QLabel("Loan Calculator", self) # setting geometry to the head head.setGeometry(0, 10, 400, 60) # font font = QFont('Times', 15) font.setBold(True) font.setItalic(True) font.setUnderline(True) # setting font to the head head.setFont(font) # setting alignment of the head head.setAlignment(Qt.AlignCenter) # setting color effect to the head color = QGraphicsColorizeEffect(self) color.setColor(Qt.darkCyan) head.setGraphicsEffect(color) # creating a interest label i_label = QLabel("Annual Interest", self) # setting properties to the interest label i_label.setAlignment(Qt.AlignCenter) i_label.setGeometry(20, 100, 170, 40) i_label.setStyleSheet("QLabel" "{" "border : 2px solid black;" "background : rgba(70, 70, 70, 35);" "}") i_label.setFont(QFont('Times', 9)) # creating a QLineEdit object to get the interest self.rate = QLineEdit(self) # accepting only number as input onlyInt = QIntValidator() self.rate.setValidator(onlyInt) # setting properties to the rate line edit self.rate.setGeometry(200, 100, 180, 40) self.rate.setAlignment(Qt.AlignCenter) self.rate.setFont(QFont('Times', 9)) # creating a number of years label n_label = QLabel("Years ", self) # setting properties to the years label n_label.setAlignment(Qt.AlignCenter) n_label.setGeometry(20, 150, 170, 40) n_label.setStyleSheet("QLabel" "{" "border : 2px solid black;" "background : rgba(70, 70, 70, 35);" "}") n_label.setFont(QFont('Times', 9)) # creating a QLineEdit object to get the years self.years = QLineEdit(self) # accepting only number as input onlyInt = QIntValidator() self.years.setValidator(onlyInt) # setting properties to the rate line edit self.years.setGeometry(200, 150, 180, 40) self.years.setAlignment(Qt.AlignCenter) self.years.setFont(QFont('Times', 9)) # creating a loan amount label a_label = QLabel("Amount", self) # setting properties to the amount label a_label.setAlignment(Qt.AlignCenter) a_label.setGeometry(20, 200, 170, 40) a_label.setStyleSheet("QLabel" "{" "border : 2px solid black;" "background : rgba(70, 70, 70, 35);" "}") a_label.setFont(QFont('Times', 9)) # creating a QLineEdit object to get the amount self.amount = QLineEdit(self) # accepting only number as input onlyInt = QIntValidator() self.amount.setValidator(onlyInt) # setting properties to the rate line edit self.amount.setGeometry(200, 200, 180, 40) self.amount.setAlignment(Qt.AlignCenter) self.amount.setFont(QFont('Times', 9)) # creating a push button calculate = QPushButton("Compute Payment", self) # setting geometry to the push button calculate.setGeometry(125, 270, 150, 40) # adding action to the calculate button calculate.clicked.connect(self.calculate_action) # creating a label to show monthly payment self.m_payment = QLabel(self) # setting properties to m payment label self.m_payment.setAlignment(Qt.AlignCenter) self.m_payment.setGeometry(50, 340, 300, 60) self.m_payment.setStyleSheet("QLabel" "{" "border : 3px solid black;" "background : white;" "}") self.m_payment.setFont(QFont('Arial', 11)) # creating a label to show monthly payment self.y_payment = QLabel(self) # setting properties to y payment label self.y_payment.setAlignment(Qt.AlignCenter) self.y_payment.setGeometry(50, 410, 300, 60) self.y_payment.setStyleSheet("QLabel" "{" "border : 3px solid black;" "background : white;" "}") self.y_payment.setFont(QFont('Arial', 11)) # method for calculating monthly # and annually payments def calculate_action(self): # getting annual interest rate annualInterestRate = self.rate.text() # if there is no number is entered if len(annualInterestRate) == 0 or annualInterestRate == '0': return # getting number of years numberOfYears = self.years.text() # if there is no number is entered if len(numberOfYears) == 0 or numberOfYears == '0': return # getting loan amount loanAmount = self.amount.text() # if there is no number is entered if len(loanAmount) == 0 or loanAmount == '0': return # converting text to int annualInterestRate = int(annualInterestRate) numberOfYears = int(numberOfYears) loanAmount = int(loanAmount) # getting monthly interest rate monthlyInterestRate = annualInterestRate / 1200 # calculating monthly payment monthlyPayment = loanAmount * monthlyInterestRate / (1 - 1 / (1 + monthlyInterestRate) ** (numberOfYears * 12)) # setting formatting monthlyPayment = "{:.2f}".format(monthlyPayment) # setting text to the label self.m_payment.setText("Monthly Payment : " + str(monthlyPayment)) # getting total payment totalPayment = float(monthlyPayment) * 12 * numberOfYears totalPayment = "{:.2f}".format(totalPayment) # setting text to the label self.y_payment.setText("Total Payment : " + str(totalPayment))# create pyqt5 appApp = QApplication(sys.argv)# create the instance of our Windowwindow = Window()# start the appsys.exit(App.exec()) |
Output :
