Calculator In Python

# Calculator in Python
# --------------------

# -*-coding:UTF-8 -*

import os

# Introduction

print ("Calclulator in Python\n")
print ("Available :\n")
print ("+\n-\n/\n*\n**\n%\n")
result = 0
stop = False
choice = ""


# Main Loop
while stop == False:

    # Take Input
    # First Number

    while True:
        first_number = input("Enter First Number : ")
        if first_number.isdigit():
            first_number = float(first_number)
            break

    # Operation

    operation = input("Operation ? ")

    # Second Number
    while True:
        second_number = input("Enter Second Number : ")
        if second_number.isdigit():
            second_number = float(second_number)
            break

    # Calculation

    if operation == "+":
        result = first_number + second_number
    elif operation == "-":
        result = first_number - second_number
    elif operation == "*":
        result = first_number * second_number
    elif operation == "/":
        result = first_number / second_number
    elif operation == "**":
        result = first_number ** second_number
    elif operation == "%":
        result = first_number % second_number
    else:
        print ("That's not an operation !")

    # Result

    print (first_number," ",operation," ",second_number," equals: ",result,".")

    # Asking for ReCalculation
    choice = input("Do you want to start over ?(O/N): ")
    if choice == "O":
        continue
    else:
        stop = True



os.system("pause")