def int_check(question, low , high):
    """checks user enter an integer / foat that is more than zero"""



    error = f"opps - please enter an interger between {low} and {high}."


    while True:

        try:
            # changing the responce to an integer and check that it is more than 0
            response = int (input(question))

            if low <= response <= high:
                return response
            else:
                print(error)

        except ValueError:
            print (error)

def not_blank(question):
    """checks that the users reponce is not blank"""

    while True:
        response = input(question)

        if response !="":
            return response

        print("Sorry, this cant be blank. please try again.\n")

def string_check(question, valid_ans_list=('yes', 'no'),
                 num_letter=1):
    """checks the users enter the full word or the first letter of a word
    from a list of responces"""

    while True:
        response = input(question).lower()


        for item in valid_ans_list:


            #checks if the response is the entire word
            if response == item:
                return item

            #checks if the responce is the first letter
            elif response == item [:num_letter]:
                return item

        print(f"please choose an option from {valid_ans_list}")

#main routine gose here

#intialise variables / non-default options for string checker

payment_ans = ('cash', 'credit')

#price list
CHILD_PRICE = 7.50
ADULT_PRICE = 10.50
SENIOR_PRICE = 6.50
#SERPLUS (5%)
CREDIT_SURCHARGE=0.05
#loop for testing
while True:
    print()

    name= not_blank("name: ")


    age = int_check("Age: ")


    if age <12:
        print(f"{name} is too young")
        continue
    elif 12 <= age<16:
        ticket_price=CHILD_PRICE

    elif 16 <= age <65:
        ticket_price = ADULT_PRICE
    elif 65 <= age <121:
        ticket_price = SENIOR_PRICE
    else:
        print(f"{name} is to old")
        continue

    pay_method = string_check("payment ,method:", payment_ans, 2)

    if pay_method == "cash":
        surcharge = 0
    else:
        surcharge= ticket_price*CREDIT_SURCHARGE

    #total payabable

    total_to_pay = ticket_price + surcharge

    print(f"{name}'s ticket cost ${ticket_price:.2f}, they paid by {pay_method}"
          f"so the surcharge is ${surcharge:.2f}\n"
          f"the total payable is ${total_to_pay:.2f}\n")