2022.7.16.

import sys
from PyQt5.QtWidgets import (QApplication, QPushButton, QWidget, QGridLayout, QLineEdit,  QTextEdit, QVBoxLayout, QHBoxLayout)
from PyQt5.QtGui import *
class MyApp(QWidget):

    def __init__(self):
        super().__init__()
        self.initUI()
        self.X = 0
        self.te = ''

    def initUI(self):
        hbox = QHBoxLayout()
        self.y = QTextEdit()
        self.y.setStyleSheet('background-color: rgb(50, 50, 50); color: white')
        hbox.addWidget(self.y)

        vbox = QVBoxLayout()
        self.x = QLineEdit()
        self.x.setStyleSheet('background-color: rgb(50, 50, 50); color: white; font: 18pt')
        vbox.addWidget(self.x)
        self.x.setText('0')

        grid = QGridLayout()
        for i in range(4):
            for j in range(3):
                if i * 3 + j >= 10:
                    break
                btn = QPushButton(str(9 - (i * 3 + j)))
                btn.setCheckable(False)
                btn.clicked.connect(self.onChanged)
                btn.setStyleSheet('QPushButton {background-color: rgb(110, 110, 110); color: white; font: 17pt}')
                btn.toggle()

                if 9 - (i * 3 + j) == 0:
                    grid.addWidget(btn, 4, 0)
                else:
                    grid.addWidget(btn, i + 1, 2 - j)

        btn1 = QPushButton('+')
        btn1.setCheckable(False)
        btn1.clicked.connect(self.plus)
        btn1.setStyleSheet('QPushButton {background-color: rgb(230, 167, 99); color: white; font: 17pt}')
        btn1.toggle()
        grid.addWidget(btn1, 3, 3)

        btn2 = QPushButton('-')
        btn2.setCheckable(False)
        btn2.clicked.connect(self.minus)
        btn2.setStyleSheet('QPushButton {background-color: rgb(230, 167, 99); color: white; font: 17pt}')
        btn2.toggle()
        grid.addWidget(btn2, 2, 3)

        btn3 = QPushButton('x')
        btn3.setCheckable(False)
        btn3.clicked.connect(self.multiple)
        btn3.setStyleSheet('QPushButton {background-color: rgb(230, 167, 99); color: white; font: 17pt}')
        btn3.toggle()
        grid.addWidget(btn3, 1, 3)

        btn4 = QPushButton('÷')
        btn4.setCheckable(False)
        btn4.clicked.connect(self.divide)
        btn4.setStyleSheet('QPushButton {background-color: rgb(230, 167, 99); color: white; font: 17pt}')
        btn4.toggle()
        grid.addWidget(btn4, 0, 3)

        btn5 = QPushButton('=')
        btn5.setCheckable(False)
        btn5.setStyleSheet('QPushButton {background-color: rgb(230, 167, 99); color: white; font: 17pt}')
        btn5.toggle()
        btn5.clicked.connect(self.equal)
        grid.addWidget(btn5, 4, 3)

        btn6 = QPushButton('AC')
        btn6.setCheckable(False)
        btn6.setStyleSheet('QPushButton {background-color: rgb(80, 80, 80); color: white; font: 17pt}')
        btn6.toggle()
        btn6.clicked.connect(self.reset)
        grid.addWidget(btn6, 0, 0)

        btn7 = QPushButton('+/-')
        btn7.setCheckable(False)
        btn7.setStyleSheet('QPushButton {background-color: rgb(80, 80, 80); color: white; font: 17pt}')
        btn7.toggle()
        btn7.clicked.connect(self.sign)
        grid.addWidget(btn7, 0, 1)

        btn8 = QPushButton('⌫')
        btn8.setCheckable(False)
        btn8.setStyleSheet('QPushButton {background-color: rgb(80, 80, 80); color: white; font: 17pt}')
        btn8.toggle()
        btn8.clicked.connect(self.delete)
        grid.addWidget(btn8, 0, 2)

        vbox.addLayout(grid)

        hbox.addLayout(vbox)

        self.setLayout(hbox)

        self.setWindowTitle('calculator')
        pal = QPalette()
        pal.setColor(QPalette.Background, QColor(50, 50, 50))
        self.setAutoFillBackground(True)
        self.setPalette(pal)
        self.setGeometry(300, 300, 300, 200)
        self.show()

    def onChanged(self):
        btn = self.sender()
        txt = int(self.x.text())
        txt *= 10
        txt += int(btn.text())
        self.x.setText(str(txt))

    def plus(self):
        self.X = 1
        self.number = int(self.x.text())
        self.x.setText('0')

    def minus(self):
        self.X = 2
        self.number = int(self.x.text())
        self.x.setText('0')

    def multiple(self):
        self.X = 3
        self.number = int(self.x.text())
        self.x.setText('0')

    def divide(self):
        self.X = 4
        self.number = int(self.x.text())
        self.x.setText('0')

    def equal(self):
        num = int(self.x.text())
        if self.X == 1:
            self.x.setText(str(self.number + num))
            self.te = (str(self.number) + '+' + str(num) + '=' + str(self.number + num))
        elif self.X == 2:
            self.x.setText(str(self.number - num))
            self.te = (str(self.number) + '-' + str(num) + '=' + str(self.number - num))
        elif self.X == 3:
            self.x.setText(str(self.number * num))
            self.te = (str(self.number) + 'x' + str(num) + '=' + str(self.number * num))
        elif self.X == 4:
            if num == 0:
                self.x.setText(str(self.number))
                self.te = (str(self.number) + '÷' + str(num) + '=' + str(self.number))
            else:
                self.x.setText(str(self.number // num))
                self.te = (str(self.number) + '÷' + str(num) + '=' + str(self.number // num))
        self.y.setText(self.te)
        self.number = 0
        self.X = 0

    def reset(self):
        self.x.setText('0')
        self.number = 0

    def sign(self):
        self.x.setText(str(-(int(self.x.text()))))

    def delete(self):
        self.x.setText(str((int(self.x.text())) // 10))

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = MyApp()
    sys.exit(app.exec_())