I have a young friend of mine who is starting to learn python in school and asked me to give him a little assignment (I am in no way a teacher nor a python expert but I accepted).

At first I thought it would be fun to start with a bit of parsing for the operation's input, like :

Enter your operation : 3+3

But it seemed a bit overwhelming for him so we agreed to separate it in three parts (first number, operand and second number)

I did a little correction but I find it clumsy and the point of the exercice is to show him some good practices...

So here is my code :

calculate = True
while calculate:
    try:
        number1 = float(input("Enter the first number : "))
    except ValueError:
            print("Incorrect value")
            exit()
    symbol = input("Enter the operation symbol (+,-,/,*,%) : ")
    try:
        number2 = float(input("Enter the second number : "))
    except ValueError:
            print("Incorrect value")
            exit()
    operande = ["+", "-", "*", "/", "%"]
    resSentence = "Result of operation \"{} {} {}\" is :".format(number1, symbol, number2)
    if symbol not in operande:
        print("Incorrect symbol")
    elif symbol == "+":
        print(resSentence, number1 + number2)
    elif symbol == "-":
        print(resSentence, number1 - number2)
    elif symbol == "*":
        print(resSentence, number1 * number2)
    elif symbol == "/":
        print(resSentence, number1 / number2)
    elif symbol == "%":
        print(resSentence, number1 % number2)
    restart = input("Do you want to do another calcul (Y/n) ? ")
    while restart.lower() != "y" and restart.lower() != "n":
        print(restart.lower(), restart.lower(), restart.lower()=="n")
        restart = input("Please, enter \"y\" to continue or \"n\" to exit the program : ")
    if restart.lower() == "n":
        calculate = False

I would have wanted to do a loop when number1 or number2 is not a valid float until the user enter a valid value but I did not found a clean way to do it, so I would gladly accept advices about this (even tho I know this is not a question for this stack exchange, a good pythonic way for doing this would be cool :) ).