Error handling in python for custom exceptions

Question

I am trying to put an error exception on these operators. Basically i want to throw an error if anything other than the items on the list is inputted. I know why this code is not working but i am not sure how to fix it. Please help me make this work. Thank you

while True:
        sign = ["+", "-" , "/" , "*"]
        try:
            operation_type=(input("what operation type you want to do?"))
            for i in range (len(sign)) :
                
                if (operation_type!= sign[i]):
                    print ("pass")
                    raise Invalid
                    i+=1
                break
        except Invalid:
            print("Please input + or - or / or *")

Answer 1

Here is what I found that worked best (I have included comments which should explain everything):

sign = ["+", "-" , "/" , "*"]

while True:
    operation_type=input("what operation type you want to do?")

    if operation_type in sign:#If the input is in one of the operations in sign, then quit.
        print(operation_type, 'passed')
        break#Break out of checking loop, as the requirement is met

    print('that is not the required operation')#Essentially your exception
         
 print('program done')

I hope this is what you are looking for!