Building Calculator using PyQt5 in Python

In this article we will see how we can create a calculator using PyQt5,A calculator is something used for making mathematical calculations, in particular a small electronic device with a keyboard and a visual display. below is the how the calculator will looks like

GUI implementation steps 

• Create a label to show the numbers and the output and set its geometry 
• Align the label text from right side and increase the font size of it 
• Create push buttons for the numbers from 0 to 9 and set their geometry in the proper order 
• Create operator push button example for addition, subtraction etc 
• Add a color effect to the equals button to highlight it

Back end implementation steps

• Add action to each button 
• Inside the actions of each button except the equals to action, append the text of the label with the respective number or the operator 
• Inside the equals to action get the text of the label and start the try except block 
• Inside the try block use eval method on the label text to get the ans and set the answer to the label 
• Inside the except block set “Wrong Input” as text 
• For delete action make the last character removed from the label and for the clear action set the whole text to blank.

Below is the implementation 

Python3

# importing libraries
from PyQt5.QtWidgets import *
from PyQt5 import QtCore, QtGui
from PyQt5.QtGui import *
from PyQt5.QtCore import *

import sys


class Window(QMainWindow):

    def __init__(self):
        super().__init__()

        # setting title
        self.setWindowTitle("Python ")

        # setting geometry
        self.setGeometry(100, 100, 360, 350)

        # calling method
        self.UiComponents()

        # showing all the widgets
        self.show()

        # method for widgets
    def UiComponents(self):

        # creating a label
        self.label = QLabel(self)

        # setting geometry to the label
        self.label.setGeometry(5, 5, 350, 70)

        # creating label multi line
        self.label.setWordWrap(True)

        # setting style sheet to the label
        self.label.setStyleSheet("QLabel"
                                 "{"
                                 "border : 4px solid black;"
                                 "background : white;"
                                 "}")

        # setting alignment to the label
        self.label.setAlignment(Qt.AlignRight)

        # setting font
        self.label.setFont(QFont('Arial', 15))


        # adding number button to the screen
        # creating a push button
        push1 = QPushButton("1", self)

        # setting geometry
        push1.setGeometry(5, 150, 80, 40)

        # creating a push button
        push2 = QPushButton("2", self)

        # setting geometry
        push2.setGeometry(95, 150, 80, 40)

        # creating a push button
        push3 = QPushButton("3", self)

        # setting geometry
        push3.setGeometry(185, 150, 80, 40)

        # creating a push button
        push4 = QPushButton("4", self)

        # setting geometry
        push4.setGeometry(5, 200, 80, 40)

        # creating a push button
        push5 = QPushButton("5", self)

        # setting geometry
        push5.setGeometry(95, 200, 80, 40)

        # creating a push button
        push6 = QPushButton("5", self)

        # setting geometry
        push6.setGeometry(185, 200, 80, 40)

        # creating a push button
        push7 = QPushButton("7", self)

        # setting geometry
        push7.setGeometry(5, 250, 80, 40)

        # creating a push button
        push8 = QPushButton("8", self)

        # setting geometry
        push8.setGeometry(95, 250, 80, 40)

        # creating a push button
        push9 = QPushButton("9", self)

        # setting geometry
        push9.setGeometry(185, 250, 80, 40)

        # creating a push button
        push0 = QPushButton("0", self)

        # setting geometry
        push0.setGeometry(5, 300, 80, 40)

        # adding operator push button
        # creating push button
        push_equal = QPushButton("=", self)

        # setting geometry
        push_equal.setGeometry(275, 300, 80, 40)

        # adding equal button a color effect
        c_effect = QGraphicsColorizeEffect()
        c_effect.setColor(Qt.blue)
        push_equal.setGraphicsEffect(c_effect)

        # creating push button
        push_plus = QPushButton("+", self)

        # setting geometry
        push_plus.setGeometry(275, 250, 80, 40)

        # creating push button
        push_minus = QPushButton("-", self)

        # setting geometry
        push_minus.setGeometry(275, 200, 80, 40)

        # creating push button
        push_mul = QPushButton("*", self)

        # setting geometry
        push_mul.setGeometry(275, 150, 80, 40)

        # creating push button
        push_div = QPushButton("/", self)

        # setting geometry
        push_div.setGeometry(185, 300, 80, 40)

        # creating push button
        push_point = QPushButton(".", self)

        # setting geometry
        push_point.setGeometry(95, 300, 80, 40)


        # clear button
        push_clear = QPushButton("Clear", self)
        push_clear.setGeometry(5, 100, 200, 40)

        # del one character button
        push_del = QPushButton("Del", self)
        push_del.setGeometry(210, 100, 145, 40)

        # adding action to each of the button
        push_minus.clicked.connect(self.action_minus)
        push_equal.clicked.connect(self.action_equal)
        push0.clicked.connect(self.action0)
        push1.clicked.connect(self.action1)
        push2.clicked.connect(self.action2)
        push3.clicked.connect(self.action3)
        push4.clicked.connect(self.action4)
        push5.clicked.connect(self.action5)
        push6.clicked.connect(self.action6)
        push7.clicked.connect(self.action7)
        push8.clicked.connect(self.action8)
        push9.clicked.connect(self.action9)
        push_div.clicked.connect(self.action_div)
        push_mul.clicked.connect(self.action_mul)
        push_plus.clicked.connect(self.action_plus)
        push_point.clicked.connect(self.action_point)
        push_clear.clicked.connect(self.action_clear)
        push_del.clicked.connect(self.action_del)


    def action_equal(self):

        # get the label text
        equation = self.label.text()

        try:
            # getting the ans
            ans = eval(equation)

            # setting text to the label
            self.label.setText(str(ans))

        except:
            # setting text to the label
            self.label.setText("Wrong Input")

    def action_plus(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + " + ")

    def action_minus(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + " - ")

    def action_div(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + " / ")

    def action_mul(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + " * ")

    def action_point(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + ".")

    def action0(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + "0")

    def action1(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + "1")

    def action2(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + "2")

    def action3(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + "3")

    def action4(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + "4")

    def action5(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + "5")

    def action6(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + "6")

    def action7(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + "7")

    def action8(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + "8")

    def action9(self):
        # appending label text
        text = self.label.text()
        self.label.setText(text + "9")

    def action_clear(self):
        # clearing the label text
        self.label.setText("")

    def action_del(self):
        # clearing a single digit
        text = self.label.text()
        print(text[:len(text)-1])
        self.label.setText(text[:len(text)-1])


# create pyqt5 app
App = QApplication(sys.argv)

# create the instance of our Window
window = Window()

# start the app
sys.exit(App.exec())

Output :