reusing code with function

import math

def do_calculation():   # function that replace some code in add and subtract operations
    print("lets " + command + " some numbers")
    input1 = input("Number 1> ")
    input2 = input("Number 2> ")
    number1 = int(input1)
    number2 = int(input2)
    if command == "add":
        result = number1 + number2
        operator = " + "
    elif command == "subtract":
        result = number1 - number2
        operator = " - "
    output = str(result)
    print(input1 + operator + input2 + " = " + output)


finished = False
while finished == False:

    print()
    print("Hi, I am Atom, your personal bot.")
    print("You can select one word of the menu, writing the word:")
    print("add   subtract   multiply   divide   volume   average   shopping   bye")
    command = input("How can I help you? ")

    # This if works when the word of the menu is wrong, giving a message "Sorry, I don't understand."
    if command !="add" and command !="subtract" and command !="multiply" and command !="divide" and command !="volume" and command !="average" and command !="shopping" and command != "bye":
        print("Sorry, I don't understand.")

    elif command == "add" or command == "plus":   # Adding code with function do_calculation() in line 30
        do_calculation()

    elif command == "subtract":   # Adding code with function do_calculation() in line 36
        do_calculation()

    elif command == "multiply" or command == "multiplication":   # Adding code to multiply in lines 38-46
        print("lets multiply two numbers")
        input1 = input("Number 1> ")
        input2 = input("Number 2> ")
        number1 = float(input1)
        number2 = float(input2)
        result = number1 * number2
        output = str(result)
        print(input1 + " * " + input2 + " = " + output)

    elif command == "divide" or command == "division":   # Adding code to divide in lines 48-56
        print("lets divide two numbers")
        input1 = input("Number 1> ")
        input2 = input("Number 2> ")
        number1 = float(input1)
        number2 = float(input2)
        result = number1 / number2
        output = str(result)
        print(input1 + " / " + input2 + " = " + output)

    elif command == "Volume" or command == "volume":   # Adding code to volume in lines 58-67
        print("lets calculate volume of cylinder with 2 values, ratio and high in cms.")
        input1 = input("ratio > ")
        input2 = input("high > ")
        ratio = float(input1)
        high = float(input2)
        #pi1 = 3.14
        result = math.pi * ratio * ratio * high
        output = str(result)
        print("volume of cylinder = " + output + " cms^3")

    elif command == "average" or command == "Average":   # Adding code to average in lines 69-78
        print("lets calculate the average of some numbers!")
        how_many = input("How many numbers > ")
        how_many = int(how_many)
        total = 0
        for number_count in range(how_many):
            number = input("Enter number " + str(number_count + 1) + "> ")
            total = total + int(number)
        result = total/ how_many
        print("the average = " + str(result))

    elif command == "shopping" or command == "Shopping":   # Adding code to shopping in lines 80-94
        shopping = []
        how_many = input("how many items of shopping do you have? ")
        how_many = int(how_many)
        total = 0
        for item_number in range (how_many):
            item = input("What is the value of item " + str(item_number + 1) + "? ")
            shopping.append(item)
            total = total + float(item)
        print(shopping)
        print("Total shopping = " + str(total))

        for item in shopping:
            print(item)
        print("You have " + str(len(shopping)) + " items in your shopping list" + " and the total shopping is = " + str(total))

    else:
        if command == "bye" or command == "Bye":
            finished = True
            print("session finished")

print("Bye")