Помогите разобраться!

У меня такая проблема возникла, что когда я запускаю код вроде бы всё работает, но когда время доходит до переменной sign. Не всё корректно работает, если вводить в переменую sign (fct или factorial), то всё работает замечательно, а если +, -, *, **, //, /, sqrt

# Welcome, my Calculator 1.0 Edition & nikEgoEDITION
# Made by nikEgo

# https://github.com/nikEgo/Calculator-in-Python-Edition

from math import sqrt as sq, factorial as fct

def add(a, b): return a + b
def minn(a, b): return a - b
def mult(a, b): return a * b
def div(a, b):
  warning = "Так делать нельзя!!"
  if b != 0:
    if b > a:
      return round(a / b, 3)
    else:
      return round(a / b, 5)
  else:
    return warning
def powMy(a, b): return a ** b 

def main():
    loop = True
    first_number, second_number, sign = 0, 0, ''
    while loop:
        while True:
            current_state = True
            try: first_number = float(int(input("Input first number: ")))
            except ValueError: current_state = False
            finally:
                if current_state:
                    break
        while True:
            current_state = True
            try: second_number = float(int(input("Input second number: ")))
            except ValueError: current_state = False
            finally:
                if current_state:
                    break
        while True:
            current_state = True
            try: sign = input("Input sign: ")
            finally:
              operations = ['+', '-', '*', '/', '**', '//', 'sqrt', 'factorial', 'fct']
              for operation in operations:
                if operation == sign: current_state = True
                else: current_state = False

            if current_state == True: break

        loop = False

    if sign == '+': print(add(first_number, second_number))
    elif sign == '-': print(minn(first_number, second_number))
    elif sign == '*': print(mult(first_number, second_number))
    elif sign == '/': print(div(first_number, second_number))
    elif sign == '**': print(powMy(first_number, second_number))
    elif sign == 'sqrt': print(*[sq(first_number), sq(second_number)])
    elif sign == 'factorial' or sign == 'fct': print(*[fct(int(first_number)), fct(int(second_number))])

if __name__ == '__main__':
    main()