Python Program - Simple Calculator

Simple Calculator Program

Here is a simple Python program to create a calculator that can perform basic arithmetic operations like addition [1], subtraction, multiplication, or division.

Objective of This Program

The objective of this program is to create a simple calculator that can perform basic arithmetic operations such as addition [1], subtraction, multiplication, and division.

Pseudocode for This Program

1. Define the four arithmetic functions:

    1.1 add(x, y) - returns the sum of x and y.

    1.2 subtract(x, y) - returns the difference of x and y.

    1.3 multiply(x, y) - returns the product of x and y.

    1.4 divide(x, y) - returns the quotient of x and y.

2. Print a menu of available operations to the user:

    2.1 "Select operation."

    2.2 "1. Add"

    2.3 "2. Subtract"

    2.4 "3. Multiply"

    2.5 "4. Divide"

3. Take the user's choice of operation as input:

    3.1 Read the user's input into the variable `choice`.

4. Take the first number as input:

    4.1 Read the user's input into the variable `num1`.

    4.2 Convert `num1` from string to integer.

5. Take the second number as input:

    5.1 Read the user's input into the variable `num2`.

    5.2 Convert `num2` from string to integer.

6. Perform the selected operation and print the result:

    6.1 If `choice` is "1", call the `add` function with `num1` and `num2` as arguments, and print the result.

    6.2 If `choice` is "2", call the `subtract` function with `num1` and `num2` as arguments, and print the result.

    6.3 If `choice` is "3", call the `multiply` function with `num1` and `num2` as arguments, and print the result.

    6.4 If `choice` is "4", call the `divide` function with `num1` and `num2` as arguments, and print the result.

    6.5 If `choice` is none of the above, print an error message "Invalid input".

Program Source Code

---

# Create a calculator

# Define functions
def add(x, y):
   return x + y

def subtract(x, y):
   return x - y

def multiply(x, y):
   return x * y

def divide(x, y):
   return x / y

# Take input from the user
print("Select operation.")
print("1.Add")
print("2.Subtract")
print("3.Multiply")
print("4.Divide")

choice = input("Enter choice(1/2/3/4):")

num1 = int(input("Enter first number: "))
num2 = int(input("Enter second number: "))

if choice == '1':
   print(num1,"+",num2,"=", add(num1,num2))

elif choice == '2':
   print(num1,"-",num2,"=", subtract(num1,num2))

elif choice == '3':
   print(num1,"*",num2,"=", multiply(num1,num2))

elif choice == '4':
   print(num1,"/",num2,"=", divide(num1,num2))
else:
   print("Invalid input")

---

Console Output 

In this example, the user selected option 3 (Multiply) and entered 5 as the first number and 7 as the second number. The program then performed the multiplication operation and displayed the result, which is 35. 

Image by 200 Degrees from Pixabay