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Calculator-Python with GUI

PasiduPerera
Level Up Coding
Published in
10 min readDec 2, 2020

--

Don’t get intimidated by the code, most of this was generated by me when I converted my UI file from QtDesigner into python code using the terminal (and scroll past it for the description).

valids = {'x': '[\'x\', \'+\', \'÷\', \'^\']', '+': '[\'x\', \'+\', \'÷\', \'^\']',
          '/': '[\'x\', \'+\', \'÷\', \'^\']',
          '^': '[\'x\', \'+\', \'÷\', \'^\']', '-': '[\'x\',\'÷\', \'^\']',
          '(': '[\'x\', \'+\', \'÷\', \'^\',\'(\']'}from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtWidgets import QMainWindow


class Ui_MainWindow(QMainWindow):
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(300, 450)
        palette = QtGui.QPalette()
        brush = QtGui.QBrush(QtGui.QColor(165, 163, 158))
        brush.setStyle(QtCore.Qt.SolidPattern)

        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.WindowText, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 255))
        brush.setStyle(QtCore.Qt.SolidPattern)

        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.Base, brush)
        brush = QtGui.QBrush(QtGui.QColor(146, 146, 152))
        brush.setStyle(QtCore.Qt.SolidPattern)

        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.Window, brush)
        brush = QtGui.QBrush(QtGui.QColor(165, 163, 158))
        brush.setStyle(QtCore.Qt.SolidPattern)

        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.WindowText, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 255))
        brush.setStyle(QtCore.Qt.SolidPattern)

        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Base, brush)
        brush = QtGui.QBrush(QtGui.QColor(146, 146, 152))
        brush.setStyle(QtCore.Qt.SolidPattern)

        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Window, brush)
        brush = QtGui.QBrush(QtGui.QColor(120, 120, 120))
        brush.setStyle(QtCore.Qt.SolidPattern)

        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.WindowText, brush)
        brush = QtGui.QBrush(QtGui.QColor(146, 146, 152))
        brush.setStyle(QtCore.Qt.SolidPattern)

        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.Base, brush)
        brush = QtGui.QBrush(QtGui.QColor(146, 146, 152))
        brush.setStyle(QtCore.Qt.SolidPattern)

        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.Window, brush)
        MainWindow.setPalette(palette)
        MainWindow.setAutoFillBackground(False)

        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.CalcScreen = QtWidgets.QLabel(self.centralwidget)
        self.CalcScreen.setGeometry(QtCore.QRect(10, 15, 280, 91))
        palette = QtGui.QPalette()
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.WindowText, brush)
        brush = QtGui.QBrush(QtGui.QColor(211, 211, 240))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.Button, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 255))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.Light, brush)
        brush = QtGui.QBrush(QtGui.QColor(233, 233, 247))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.Midlight, brush)
        brush = QtGui.QBrush(QtGui.QColor(105, 105, 120))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.Dark, brush)
        brush = QtGui.QBrush(QtGui.QColor(141, 141, 160))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.Mid, brush)
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.Text, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 255))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.BrightText, brush)
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.ButtonText, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 255))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.Base, brush)
        brush = QtGui.QBrush(QtGui.QColor(211, 211, 240))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.Window, brush)
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.Shadow, brush)
        brush = QtGui.QBrush(QtGui.QColor(233, 233, 247))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.AlternateBase, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 220))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.ToolTipBase, brush)
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Active, QtGui.QPalette.ToolTipText, brush)
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.WindowText, brush)
        brush = QtGui.QBrush(QtGui.QColor(211, 211, 240))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Button, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 255))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Light, brush)
        brush = QtGui.QBrush(QtGui.QColor(233, 233, 247))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Midlight, brush)
        brush = QtGui.QBrush(QtGui.QColor(105, 105, 120))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Dark, brush)
        brush = QtGui.QBrush(QtGui.QColor(141, 141, 160))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Mid, brush)
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Text, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 255))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.BrightText, brush)
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.ButtonText, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 255))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Base, brush)
        brush = QtGui.QBrush(QtGui.QColor(211, 211, 240))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Window, brush)
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.Shadow, brush)
        brush = QtGui.QBrush(QtGui.QColor(233, 233, 247))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.AlternateBase, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 220))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.ToolTipBase, brush)
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Inactive, QtGui.QPalette.ToolTipText, brush)
        brush = QtGui.QBrush(QtGui.QColor(105, 105, 120))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.WindowText, brush)
        brush = QtGui.QBrush(QtGui.QColor(211, 211, 240))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.Button, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 255))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.Light, brush)
        brush = QtGui.QBrush(QtGui.QColor(233, 233, 247))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.Midlight, brush)
        brush = QtGui.QBrush(QtGui.QColor(105, 105, 120))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.Dark, brush)
        brush = QtGui.QBrush(QtGui.QColor(141, 141, 160))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.Mid, brush)
        brush = QtGui.QBrush(QtGui.QColor(105, 105, 120))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.Text, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 255))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.BrightText, brush)
        brush = QtGui.QBrush(QtGui.QColor(105, 105, 120))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.ButtonText, brush)
        brush = QtGui.QBrush(QtGui.QColor(211, 211, 240))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.Base, brush)
        brush = QtGui.QBrush(QtGui.QColor(211, 211, 240))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.Window, brush)
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.Shadow, brush)
        brush = QtGui.QBrush(QtGui.QColor(211, 211, 240))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.AlternateBase, brush)
        brush = QtGui.QBrush(QtGui.QColor(255, 255, 220))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.ToolTipBase, brush)
        brush = QtGui.QBrush(QtGui.QColor(0, 0, 0))
        brush.setStyle(QtCore.Qt.SolidPattern)
        palette.setBrush(QtGui.QPalette.Disabled, QtGui.QPalette.ToolTipText, brush)
        self.CalcScreen.setPalette(palette)
        font = QtGui.QFont()
        font.setPointSize(15)
        font.setBold(False)
        font.setItalic(False)
        font.setWeight(50)
        font.setStrikeOut(False)
        font.setKerning(True)
        self.CalcScreen.setFont(font)
        self.CalcScreen.setAutoFillBackground(True)
        self.CalcScreen.setFrameShape(QtWidgets.QFrame.WinPanel)
        self.CalcScreen.setFrameShadow(QtWidgets.QFrame.Plain)
        self.CalcScreen.setLineWidth(1)
        self.CalcScreen.setMidLineWidth(0)
        self.CalcScreen.setText("")
        self.CalcScreen.setObjectName("CalcScreen")

        self.Calc1 = QtWidgets.QPushButton(self.centralwidget)
        self.Calc1.setGeometry(QtCore.QRect(10, 120, 50, 40))
        self.Calc1.setAutoRepeat(False)
        self.Calc1.setObjectName("Calc1")

        self.Calc2 = QtWidgets.QPushButton(self.centralwidget)
        self.Calc2.setGeometry(QtCore.QRect(70, 120, 50, 40))
        self.Calc2.setAutoRepeat(False)
        self.Calc2.setObjectName("Calc2")

        self.Calc3 = QtWidgets.QPushButton(self.centralwidget)
        self.Calc3.setGeometry(QtCore.QRect(130, 120, 50, 40))
        self.Calc3.setAutoRepeat(False)
        self.Calc3.setObjectName("Calc3")

        self.Calc4 = QtWidgets.QPushButton(self.centralwidget)
        self.Calc4.setGeometry(QtCore.QRect(10, 170, 50, 40))
        self.Calc4.setAutoRepeat(False)
        self.Calc4.setObjectName("Calc4")

        self.Calc5 = QtWidgets.QPushButton(self.centralwidget)
        self.Calc5.setGeometry(QtCore.QRect(70, 170, 50, 40))
        self.Calc5.setAutoRepeat(False)
        self.Calc5.setObjectName("Calc5")

        self.Calc6 = QtWidgets.QPushButton(self.centralwidget)
        self.Calc6.setGeometry(QtCore.QRect(130, 170, 50, 40))
        self.Calc6.setAutoRepeat(False)
        self.Calc6.setObjectName("Calc6")

        self.Calc7 = QtWidgets.QPushButton(self.centralwidget)
        self.Calc7.setGeometry(QtCore.QRect(10, 220, 50, 40))
        self.Calc7.setAutoRepeat(False)
        self.Calc7.setObjectName("Calc7")

        self.Calc8 = QtWidgets.QPushButton(self.centralwidget)
        self.Calc8.setGeometry(QtCore.QRect(70, 220, 50, 40))
        self.Calc8.setAutoRepeat(False)
        self.Calc8.setObjectName("Calc8")

        self.Calc9 = QtWidgets.QPushButton(self.centralwidget)
        self.Calc9.setGeometry(QtCore.QRect(130, 220, 50, 40))
        self.Calc9.setAutoRepeat(False)
        self.Calc9.setObjectName("Calc9")

        self.Calc0 = QtWidgets.QPushButton(self.centralwidget)
        self.Calc0.setGeometry(QtCore.QRect(70, 270, 50, 40))
        self.Calc0.setAutoRepeat(False)
        self.Calc0.setObjectName("Calc0")

        self.Enter = QtWidgets.QPushButton(self.centralwidget)
        self.Enter.setGeometry(QtCore.QRect(240, 120, 50, 40))
        self.Enter.setAutoRepeat(False)
        self.Enter.setObjectName("Enter")

        self.WDivide = QtWidgets.QPushButton(self.centralwidget)
        self.WDivide.setGeometry(QtCore.QRect(240, 160, 50, 40))
        self.WDivide.setAutoRepeat(False)
        self.WDivide.setObjectName("WDivide")

        self.WMinus = QtWidgets.QPushButton(self.centralwidget)
        self.WMinus.setGeometry(QtCore.QRect(240, 200, 50, 40))
        self.WMinus.setAutoRepeat(False)
        self.WMinus.setObjectName("WMinus")

        self.WCBracket = QtWidgets.QPushButton(self.centralwidget)
        self.WCBracket.setGeometry(QtCore.QRect(240, 240, 50, 40))
        self.WCBracket.setAutoRepeat(False)
        self.WCBracket.setObjectName("WCBracket")

        self.Backspace = QtWidgets.QPushButton(self.centralwidget)
        self.Backspace.setGeometry(QtCore.QRect(190, 120, 50, 40))
        font = QtGui.QFont()
        font.setPointSize(6)
        self.Backspace.setFont(font)
        self.Backspace.setAutoRepeat(False)
        self.Backspace.setObjectName("Backspace")

        self.WMultiply = QtWidgets.QPushButton(self.centralwidget)
        self.WMultiply.setGeometry(QtCore.QRect(190, 160, 50, 40))
        self.WMultiply.setAutoRepeat(False)
        self.WMultiply.setObjectName("WMultiply")

        self.WPlus = QtWidgets.QPushButton(self.centralwidget)
        self.WPlus.setGeometry(QtCore.QRect(190, 200, 50, 40))
        self.WPlus.setAutoRepeat(False)
        self.WPlus.setObjectName("WPlus")

        self.WOBracket = QtWidgets.QPushButton(self.centralwidget)
        self.WOBracket.setGeometry(QtCore.QRect(190, 240, 50, 40))
        self.WOBracket.setAutoRepeat(False)
        self.WOBracket.setObjectName("WOBracket")

        self.CalcDecimal = QtWidgets.QPushButton(self.centralwidget)
        self.CalcDecimal.setGeometry(QtCore.QRect(130, 270, 50, 40))
        self.CalcDecimal.setAutoRepeat(False)
        self.CalcDecimal.setObjectName("CalcDecimal")

        self.WExponent = QtWidgets.QPushButton(self.centralwidget)
        self.WExponent.setGeometry(QtCore.QRect(210, 280, 50, 40))
        self.WExponent.setAutoRepeat(False)
        self.WExponent.setObjectName("WExponent")

        MainWindow.setCentralWidget(self.centralwidget)
        self.statusbar = QtWidgets.QStatusBar(MainWindow)
        self.statusbar.setObjectName("statusbar")
        MainWindow.setStatusBar(self.statusbar)

        self.message = ''

        self.retranslateUi(MainWindow)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "Calculator"))
        self.CalcScreen.setStatusTip(_translate("MainWindow", "Calculator Screen"))
        self.CalcScreen.setWhatsThis(_translate("MainWindow", "Screen"))

        self.Calc1.setStatusTip(_translate("MainWindow", "Number 1"))
        self.Calc1.setText(_translate("MainWindow", "1"))
        self.Calc1.setShortcut(_translate("MainWindow", "1"))
        self.Calc1.clicked.connect(self.clicked)


        self.Calc2.setStatusTip(_translate("MainWindow", "Number 2"))
        self.Calc2.setText(_translate("MainWindow", "2"))
        self.Calc2.setShortcut(_translate("MainWindow", "2"))
        self.Calc2.clicked.connect(self.clicked)


        self.Calc3.setStatusTip(_translate("MainWindow", "Number 3"))
        self.Calc3.setText(_translate("MainWindow", "3"))
        self.Calc3.setShortcut(_translate("MainWindow", "3"))
        self.Calc3.clicked.connect(self.clicked)


        self.Calc4.setStatusTip(_translate("MainWindow", "Number 4"))
        self.Calc4.setText(_translate("MainWindow", "4"))
        self.Calc4.setShortcut(_translate("MainWindow", "4"))
        self.Calc4.clicked.connect(self.clicked)


        self.Calc5.setStatusTip(_translate("MainWindow", "Number 5"))
        self.Calc5.setText(_translate("MainWindow", "5"))
        self.Calc5.setShortcut(_translate("MainWindow", "5"))
        self.Calc5.clicked.connect(self.clicked)


        self.Calc6.setStatusTip(_translate("MainWindow", "Number 6"))
        self.Calc6.setText(_translate("MainWindow", "6"))
        self.Calc6.setShortcut(_translate("MainWindow", "6"))
        self.Calc6.clicked.connect(self.clicked)


        self.Calc7.setStatusTip(_translate("MainWindow", "Number 7"))
        self.Calc7.setText(_translate("MainWindow", "7"))
        self.Calc7.setShortcut(_translate("MainWindow", "7"))
        self.Calc7.clicked.connect(self.clicked)


        self.Calc8.setStatusTip(_translate("MainWindow", "Number 8"))
        self.Calc8.setText(_translate("MainWindow", "8"))
        self.Calc8.setShortcut(_translate("MainWindow", "8"))
        self.Calc8.clicked.connect(self.clicked)


        self.Calc9.setStatusTip(_translate("MainWindow", "Number 9"))
        self.Calc9.setText(_translate("MainWindow", "9"))
        self.Calc9.setShortcut(_translate("MainWindow", "9"))
        self.Calc9.clicked.connect(self.clicked)


        self.Calc0.setStatusTip(_translate("MainWindow", "Number 0"))
        self.Calc0.setText(_translate("MainWindow", "0"))
        self.Calc0.setShortcut(_translate("MainWindow", "0"))
        self.Calc0.clicked.connect(self.clicked)


        self.Enter.setStatusTip(_translate("MainWindow", "Enter"))
        self.Enter.setText(_translate("MainWindow", "Enter"))
        self.Enter.clicked.connect(self.Calculate)


        self.Enter.setShortcut(_translate("MainWindow", "Return"))


        self.WDivide.setStatusTip(_translate("MainWindow", "Divide"))
        self.WDivide.setText(_translate("MainWindow", "÷"))
        self.WDivide.clicked.connect(self.clicked)


        self.WDivide.setShortcut(_translate("MainWindow", "/"))
        self.WMinus.setStatusTip(_translate("MainWindow", "Minus"))


        self.WMinus.setText(_translate("MainWindow", "-"))
        self.WMinus.setShortcut(_translate("MainWindow", "-"))
        self.WMinus.clicked.connect(self.clicked)


        self.WCBracket.setStatusTip(_translate("MainWindow", "Closing Bracket"))
        self.WCBracket.setText(_translate("MainWindow", ")"))
        self.WCBracket.setShortcut(_translate("MainWindow", ")"))
        self.WCBracket.clicked.connect(self.clicked)


        self.Backspace.setStatusTip(_translate("MainWindow", "Backspace"))
        self.Backspace.setText(_translate("MainWindow", "Backspace"))
        self.Backspace.setShortcut(_translate("MainWindow", "Backspace"))
        self.Backspace.clicked.connect(self.delete)


        self.WMultiply.setStatusTip(_translate("MainWindow", "Multiply"))
        self.WMultiply.setText(_translate("MainWindow", "x"))
        self.WMultiply.setShortcut(_translate("MainWindow", "X"))
        self.WMultiply.clicked.connect(self.clicked)


        self.WPlus.setStatusTip(_translate("MainWindow", "Plus"))
        self.WPlus.setText(_translate("MainWindow", "+"))
        self.WPlus.setShortcut(_translate("MainWindow", "+"))
        self.WPlus.clicked.connect(self.clicked)


        self.WOBracket.setStatusTip(_translate("MainWindow", "Open Bracket"))
        self.WOBracket.setText(_translate("MainWindow", "("))
        self.WOBracket.setShortcut(_translate("MainWindow", "("))
        self.WOBracket.clicked.connect(self.clicked)


        self.CalcDecimal.setStatusTip(_translate("MainWindow", "Decimal"))
        self.CalcDecimal.setText(_translate("MainWindow", "."))
        self.CalcDecimal.setShortcut(_translate("MainWindow", "."))
        self.CalcDecimal.clicked.connect(self.clicked)


        self.WExponent.setStatusTip(_translate("MainWindow", "Exponent"))
        self.WExponent.setText(_translate("MainWindow", "^"))
        self.WExponent.setShortcut(_translate("MainWindow", "^"))
        self.WExponent.clicked.connect(self.clicked)

    def clicked(self):
        sender = self.sender()
        self.message += sender.text()
        self.CalcScreen.setText(self.message)

    def delete(self):
        self.message=self.message[:-1]
        self.CalcScreen.setText(self.message)

    def Calculate(self):
        state = True
        calculation = self.message
        for i, v in enumerate(calculation):  # iterates through the calc string
            if v in ['x', '+', '-', '÷', '^', '(']:  # doing a sign check
                if i + 1 == len(calculation):   # validating that the sign use is legal
                    state = False
                if calculation[i + 1] in valids:
                    state = False
                if calculation[-1] in ['x', '+', '-', '÷', '^','(']:
                        state = False
                if calculation.count('(') != calculation.count(')'):
                    state = False

        if state:
            self.maths()
        else:
            self.CalcScreen.setText("Invalid Input")
            self.message = ''


    def maths(self):
        calculation = '('+ str(self.message)+')'
        for i in range(len(calculation)):
            if (calculation[i]=='(' and calculation[i-1] not in ['x', '+', '-', '÷', '^', '(']) and (i != 0):
                calculation = calculation[:i]+'x'+calculation[i:]
                print(calculation)
        calculation = calculation.replace('x', '*')
        calculation = calculation.replace('÷', '/')
        calculation = calculation.replace('^', '**')

        ans = eval(calculation)
        print(ans)
        self.CalcScreen.setText(str(ans))

        self.message = ''


if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

I was recommended to make a calculator using a GUI by a computing advisor at a user and this was my attempt at making it. Please note that the majority of this code was created by Qt Designer(a UI designing app that comes with PyQt and so I won’t know exactly what those parts of the code do).

The Main Challenges that come with designing this calculator would be connecting all these buttons onto the main label which shows the calculator display, actually solving the answer since the input is going to be a string. The real way you would have to do this is by creating an Abstract Syntax Tree which in itself means you would need to go into recursion, however; python has an eval() function which means you can just run a calculation so I made use of that.

Since the code is pretty extensive, I won’t go through it line by line as I normally do but I’ll talk about the main parts of the code.

The PyQt tutorials that I followed was the Tech by Time 5 episode playlist on PyQt. Although it doesn’t go into senders and how to do the calculator parts of the program, it explains a lot of the basics of labels and buttons and how to connect them to functions.

Note: If you try this yourself, PyQt hasn’t got the best debugging which means if the program crashes due to an error while your window of PyQt is running, the only thing you are going to be given is ‘error code:…’, to try localise your error, I would advise placing occasional print statements in your code so that when it runs you can check the terminal to see which print statement it ends at and this means the error will have to be in between the print statements.

valids = {'x': '[\'x\', \'+\', \'÷\', \'^\']', '+': '[\'x\', \'+\', \'÷\', \'^\']',
          '/': '[\'x\', \'+\', \'÷\', \'^\']',
          '^': '[\'x\', \'+\', \'÷\', \'^\']', '-': '[\'x\',\'÷\', \'^\']',
          '(': '[\'x\', \'+\', \'÷\', \'^\',\'(\']'}

This valids dictionary is very important since validation of your input is a very big part of this program and I have set this dictionary so that every value is a value that can’t come after its key.

The next 300ish lines of code are all the Qt Designer autogenerated code. If you download QtDesigner, it will let you draw in your labels and buttons and set their variable names, shortcuts, positions, what they actually say etc. So that overlay which you see if you run my code was what I created on QtDesigner.

Converting UI to Python:

This is actually a lot simpler than you may expect. Go to the directory of the UI file(so wherever you have saved it in your files) and then load up the command prompt through the file manager to make sure that it is in the correct directory. Then you will write the following command:

pyuic5 -x (name of UI file).ui -o (name of python file).py

So example:

>>$ pyuic5 -x calcOverlay.ui -o Calculator.py

After that has been executed by the terminal, you should find a new python file in the same directory as the UI file which is the converted code.

Go to 9:00 if you want it better explained with visuals by Tim

Click Events:

def clicked(self):
        sender = self.sender()
        self.message += sender.text()
        self.CalcScreen.setText(self.message)

This function is what allows us to react to what button is being clicked. Many people may run into an issue because they will try pass a parameter into the clicked function however, PyQt apparently doesn’t like that. This was a problem which took me a day to solve until I read a page talking about the sender() method. The problem had been that all the clickable buttons had to use the same function so the code had to have a way of distinguishing which button had been clicked and this was the solution.

self.sender() will return the value of the text of the button that had been clicked. This now means that we can add this to the message(which is the stuff on the calculator screen) and then display them using the setText function. Note that when using setText, you will have to concatenate to string and the program won’t do this for you so when doing eval() later, you will have to convert back to string again.

self.WOBracket.clicked.connect(self.clicked)

For every button we now add this piece of code which is basically saying that when there is a click event(when the button is clicked) run the function clicked. I’m pretty sure you don’t write self.clicked with the parentheses () after it because the compiler may mistake this with actually running the function there and then so we don’t use the parentheses.

def delete(self):
        self.message=self.message[:-1]
        self.CalcScreen.setText(self.message)

The delete function has a similar purpose but now we need it in case the user makes a mistake. This code is pretty self explanatory with us indexing out the last value of the message and then displaying the result.

def Calculate(self):
        state = True
        calculation = self.message
        for i, v in enumerate(calculation):  # iterates through the calc string
            if v in ['x', '+', '-', '÷', '^', '(']:  # doing a sign check
                if i + 1 == len(calculation):   # validating that the sign use is legal
                    state = False
                if calculation[i + 1] in valids:
                    state = False
                if calculation[-1] in ['x', '+', '-', '÷', '^','(']:
                        state = False
                if calculation.count('(') != calculation.count(')'):
                    state = False

        if state:
            self.maths()
        else:
            self.CalcScreen.setText("Invalid Input")
            self.message = ''

I apologise for the formatting since medium’s line lengths are different to pythons so these look weird. This calculate function is run when the user clicks enter and this is the validation portion of the code. This is responsible for making sure the input is ‘legal’ in mathematical terms. We first set the state as True which is how I am going to track whether the maths is valid. True= the maths is correct while False= there is something which won’t work. I proceed to run this through a set of tests which you can look at and if they fail the tests, their states are reset back to false. At the end of the tests, if state is still true, I run the math function which does the actually calculations. Else, I display invalid invalid input and clear the message, if you want you can import time here and pause the program on the “Invalid Input” for a second and then reset the text back to the message instead of resetting it but that is just preference.

def maths(self):
        calculation = '('+ str(self.message)+')'
        for i in range(len(calculation)):
            if (calculation[i]=='(' and calculation[i-1] not in ['x', '+', '-', '÷', '^', '(']) and (i != 0):
                calculation = calculation[:i]+'x'+calculation[i:]
                print(calculation)
        calculation = calculation.replace('x', '*')
        calculation = calculation.replace('÷', '/')
        calculation = calculation.replace('^', '**')

        ans = eval(calculation)
        print(ans)
        self.CalcScreen.setText(str(ans))

        self.message = ''

This final calculation works out the answer. Firstly, I realised eval() reacts weirdly to calculation with brackets eg. it will crash if you run 3(3+6) because it doesn’t intuitively realise that there would be a multiply before the ( and therefore we need to add this to the calculation itself. This is what I am doing for the first 4 lines of the of the function. After that I need to convert all of my user friendly characters in the input to characters that the computer understands. This means we need to swap ‘x’ to ‘*’, ‘^’ to ‘**’ etc.

Once that has been completed, we can evaluate the answer and then set the calc display to that answer and then we are done.

Challenge: Using import math, add a pi button onto the GUI and let the user use pi in their calculations. This should follow the exact same logic as I have explained here.

Python
Coding
Computer Science
Math
Education

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PasiduPerera
Level Up Coding
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Written by PasiduPerera

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Economics Student at Cambridge University

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