在Python中使用 PyQt5 的贷款计算器
在本文中，我们将看到如何使用 PyQt5 创建贷款计算器，下图显示了贷款计算器的外观：
PyQt5是跨平台的 GUI 工具包，一组用于 Qt v5 的Python绑定。由于该库提供的工具和简单性，人们可以非常轻松地开发交互式桌面应用程序
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
下面是实现：
Python3
# importing required libraries
from PyQt5.QtWidgets import *
from PyQt5 import QtCore, QtGui
from PyQt5.QtGui import *
from PyQt5.QtCore import *
import sys
class 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 payemnt
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 app
App = QApplication(sys.argv)
# create the instance of our Window
window = Window()
# start the app
sys.exit(App.exec())输出 ：