def main():
    print("Welcome to the Calculator")
    command = input("Select command: [ + ] [ - ] [ * ] [ / ] \nНапишите exit если хотите выйти\n")
    match command: #выбор команд
        case "+":
            summ()
        case "*":
            multiplication()
        case "-":
            minus()
        case "/":
            division()
        case "exit":
            exit
        case _:
            print(KeyError("Incorrect"))
            main()
def summ(total=None):
    print("Enter number(s) to summ, enter spase to finish calculating")
    if total is None:
        try:
            total = float(input("Enter First number \n"))
        except ValueError:
            print("Enter a valid number")
            return
    while True:
        num_input = input("Enter numbers to summ or change command [ + ] [ - ] [ * ] [ / ]\n")
        if num_input == " " or num_input == "":
            print(total)
            main()
        if num_input in ["+", "-", "*", "/"]:
            if num_input == "+":
                return summ(total)
            elif num_input == "-":
                return minus(total)
            elif num_input == "*":
                return multiplication(total)
            elif num_input == "/":
                return division(total)
        try:
            number = float(num_input)
            total += number
            print(f"Total summ = {total}")
        except ValueError:
            print("Error, enter correct number")
def minus(total=None): #даём функции на первом запуске total = None чтобы присвоить ей значение первого введёного числа, чтобы не было -5 в минусе на первом вводе
    print("Enter number(s) to summ, enter spase to finish calculating")
    if total is None:
        try:
            total = float(input("Enter First number \n")) #присваивамем тоталу первое число
        except ValueError:
            print("Enter a valid number")
            return
    while True: #цикл программы с переключением функций
        num_input = input("Enter numbers to minus or change command [ + ] [ - ] [ * ] [ / ]\n")
        if num_input == " " or num_input == "": #завершение при эксите
            print(total)
            main()
        if num_input in ["+", "-", "*", "/"]: #переключение команд
            if num_input == "+":
                return summ(total)
            elif num_input == "-":
                return minus(total)
            elif num_input == "*":
                return multiplication(total)
            elif num_input == "/":
                return division(total)
        try: #трай для защиты от ввода, чтобы программа не завершалась
            number = float(num_input) #преобразование строки в число
            total -= number #отнимаем число
            print(f"Total minus = {total}") #вывод
        except ValueError:
            print("Error, enter correct number")
def multiplication(total=None):
    print("Enter number(s) to multuplicate, enter spase to finish calculating")
    print("Enter number(s) to summ, enter spase to finish calculating")
    if total is None:
        try:
            total = float(input("Enter First number \n"))
        except ValueError:
            print("Enter a valid number")
            return
    while True:
        num_input = input("Enter numbers to multiplicate or change command [ + ] [ - ] [ * ] [ / ]\n")
        if num_input == " " or num_input == "":
            print(total)
            main()
        if num_input in ["+", "-", "*", "/"]:
            if num_input == "+":
                return summ(total)
            elif num_input == "-":
                return minus(total)
            elif num_input == "*":
                return multiplication(total)
            elif num_input == "/":
                return division(total)
        try:
            number = float(num_input)
            total *= number
            print(f"Total multiplication = {total}")
        except ValueError:
            print("Error, enter correct number")
def division(total=None):
    print("Enter number(s) to summ, enter spase to finish calculating")
    if total is None:
        try:
            total = float(input("Enter First number \n"))
        except ValueError:
            print("Enter a valid number")
            return
    while True:
        num_input = input("Enter numbers to division  or change command [ + ] [ - ] [ * ] [ / ]\n")
        if num_input == " " or num_input == "":
            print(total)
            main()
        if num_input in ["+", "-", "*", "/"]:
            if num_input == "+":
                return summ(total)
            elif num_input == "-":
                return minus(total)
            elif num_input == "*":
                return multiplication(total)
            elif num_input == "/":
                return division(total)
        try:
            number = float(num_input)
            total /= number
            print(f"Total division = {total}")
        except ValueError:
            print("Error, enter correct number")

if __name__ == "__main__":
    main() #запуск функции main, основа программы