Basic calculator program using Python

Here we will be making a simple calculator in which we can perform basic arithmetic operations like addition, subtraction, multiplication, or division.

Example 1) GUI of a Calculator Which will help to add, subtract , Multiply and divide

Python

# pip install tkinter
import tkinter as tk
import tkinter.messagebox
from tkinter.constants import SUNKEN

window = tk.Tk()
window.title('Calculator-GeeksForGeeks')
frame = tk.Frame(master=window, bg="skyblue", padx=10)
frame.pack()
entry = tk.Entry(master=frame, relief=SUNKEN, borderwidth=3, width=30)
entry.grid(row=0, column=0, columnspan=3, ipady=2, pady=2)


def myclick(number):
    entry.insert(tk.END, number)


def equal():
    try:
        y = str(eval(entry.get()))
        entry.delete(0, tk.END)
        entry.insert(0, y)
    except:
        tkinter.messagebox.showinfo("Error", "Syntax Error")


def clear():
    entry.delete(0, tk.END)


button_1 = tk.Button(master=frame, text='1', padx=15,
                     pady=5, width=3, command=lambda: myclick(1))
button_1.grid(row=1, column=0, pady=2)
button_2 = tk.Button(master=frame, text='2', padx=15,
                     pady=5, width=3, command=lambda: myclick(2))
button_2.grid(row=1, column=1, pady=2)
button_3 = tk.Button(master=frame, text='3', padx=15,
                     pady=5, width=3, command=lambda: myclick(3))
button_3.grid(row=1, column=2, pady=2)
button_4 = tk.Button(master=frame, text='4', padx=15,
                     pady=5, width=3, command=lambda: myclick(4))
button_4.grid(row=2, column=0, pady=2)
button_5 = tk.Button(master=frame, text='5', padx=15,
                     pady=5, width=3, command=lambda: myclick(5))
button_5.grid(row=2, column=1, pady=2)
button_6 = tk.Button(master=frame, text='6', padx=15,
                     pady=5, width=3, command=lambda: myclick(6))
button_6.grid(row=2, column=2, pady=2)
button_7 = tk.Button(master=frame, text='7', padx=15,
                     pady=5, width=3, command=lambda: myclick(7))
button_7.grid(row=3, column=0, pady=2)
button_8 = tk.Button(master=frame, text='8', padx=15,
                     pady=5, width=3, command=lambda: myclick(8))
button_8.grid(row=3, column=1, pady=2)
button_9 = tk.Button(master=frame, text='9', padx=15,
                     pady=5, width=3, command=lambda: myclick(9))
button_9.grid(row=3, column=2, pady=2)
button_0 = tk.Button(master=frame, text='0', padx=15,
                     pady=5, width=3, command=lambda: myclick(0))
button_0.grid(row=4, column=1, pady=2)

button_add = tk.Button(master=frame, text="+", padx=15,
                       pady=5, width=3, command=lambda: myclick('+'))
button_add.grid(row=5, column=0, pady=2)

button_subtract = tk.Button(
    master=frame, text="-", padx=15, pady=5, width=3, command=lambda: myclick('-'))
button_subtract.grid(row=5, column=1, pady=2)

button_multiply = tk.Button(
    master=frame, text="*", padx=15, pady=5, width=3, command=lambda: myclick('*'))
button_multiply.grid(row=5, column=2, pady=2)

button_div = tk.Button(master=frame, text="/", padx=15,
                       pady=5, width=3, command=lambda: myclick('/'))
button_div.grid(row=6, column=0, pady=2)

button_clear = tk.Button(master=frame, text="clear",
                         padx=15, pady=5, width=12, command=clear)
button_clear.grid(row=6, column=1, columnspan=2, pady=2)

button_equal = tk.Button(master=frame, text="=", padx=15,
                         pady=5, width=9, command=equal)
button_equal.grid(row=7, column=0, columnspan=3, pady=2)

window.mainloop()

Output:

Example 2: Create a simple calculator which can perform basic arithmetic operations like addition, subtraction, multiplication, or division depending upon the user input. Approach :

• User chooses the desired operation. Options 1, 2, 3, and 4 are valid.
• Two numbers are taken and an if…elif…else branching is used to execute a particular section.
• Using functions add(), subtract(), multiply() and divide() evaluate respective operations.

Please select operation -
1. Add
2. Subtract
3. Multiply
4. Divide
Select operations form 1, 2, 3, 4 : 1
Enter first number : 20
Enter second number : 13
20 + 13 = 33

Python

# Python program for simple calculator

# Function to add two numbers
def add(num1, num2):
    return num1 + num2

# Function to subtract two numbers
def subtract(num1, num2):
    return num1 - num2

# Function to multiply two numbers
def multiply(num1, num2):
    return num1 * num2

# Function to divide two numbers
def divide(num1, num2):
    return num1 / num2

print("Please select operation -\n" \
        "1. Add\n" \
        "2. Subtract\n" \
        "3. Multiply\n" \
        "4. Divide\n")


# Take input from the user
select = int(input("Select operations form 1, 2, 3, 4 :"))

number_1 = int(input("Enter first number: "))
number_2 = int(input("Enter second number: "))

if select == 1:
    print(number_1, "+", number_2, "=",
                    add(number_1, number_2))

elif select == 2:
    print(number_1, "-", number_2, "=",
                    subtract(number_1, number_2))

elif select == 3:
    print(number_1, "*", number_2, "=",
                    multiply(number_1, number_2))

elif select == 4:
    print(number_1, "/", number_2, "=",
                    divide(number_1, number_2))
else:
    print("Invalid input")

Output:

Please select operation -
1. Add
2. Subtract
3. Multiply
4. Divide
Select operations form 1, 2, 3, 4 : 1
Enter first number : 15
Enter second number : 14
15 + 14 = 29