#functions go here

# Checks user has entered yes / no to a question
def yes_no(question):
    while True:
        response = input(question).lower()

        if response == "yes" or response == "y":
            return "yes"

        elif response == "no" or response == "n":
            return "no"

        else:
            print("PLease enter yes or no")

# checks that user response is not blank
def not_blank(question):


    while True:
        response = input(question)

        if response == "":
            print('sorry this cant be blank. Please try again')
        else:
            return response


#num checker
def num_check(question):

    while True:

        try:
            response = int(input(question))
            return response

        except ValueError:
            print("please enter a number")

# main routine starts here


# Calculate ticket price base on age
def calc_ticket_price(var_age):

    # ticket is $7.50 for under 16
    if var_age < 16:
        price = 7.5

    # ticket is $10.50 for between 16 and 64
    elif var_age < 65:
        price = 10.5

    # ticket price is $6.50 for seniors 65+
    else:
        price = 6.5

    return price


# set maximum number of tickets below
MAX_TICKETS = 3
tickets_sold = 0

# ask user if they want to see the instructions
want_instructions = yes_no("do you want to read the instructions? ")

if want_instructions == "yes" or want_instructions == "Yes":
    print("instructions go here")
elif want_instructions == "no" or want_instructions == "No":
    print("no instructions ")
else:
    print("please answer yes or no")

# loop to sell tickets
while tickets_sold < MAX_TICKETS:
    name = not_blank("Enter your name (or 'xxx' to quit) ")

    if name == 'xxx':
        break

    age = num_check("Age: ")

    if 12 <= age <= 120:
        pass
    elif age < 12:
        print("sorry your to young for this movie")
        continue
    else:
        print("that looks like a typo please try again.")
        continue

        # calculate ticket cost
    ticket_cost = calc_ticket_price(age)
    print("Age: {}, Ticket Price: ${:.2f}".format(age, ticket_cost))

    tickets_sold += 1

# Output number of tickets sold
if tickets_sold == MAX_TICKETS:
    print("Congratulations you have sold all of your tickets")
else:
    print("you have sold {} ticket/s. There is {} ticket/s remaining".format(tickets_sold, MAX_TICKETS - tickets_sold))