valid=False        ## stores variables
bartotal1=0        ##"                "
beantotal1=0       ##"                "
tunatotal1=0       ##"                "
skittletotal1=0    ##"                "
beanstock=15       ##"                "
tunastock=11       ##"                "
skittlestock=17    ##"                "
barstock=24        ##"                "
finalbill=0        ##"                "
beans1=0           ##"                "
tuna1=0            ##"                "
skittle1=0         ##"                "
bar1=0             ##"                "

channel=open('List1.txt','w') ## writes a text file with information below
beans = channel.write(('82571465 Can of Beans £0.86 15')+'n') ##adds a new                 line into text file
tuna = channel.write(('28528243 Tin of Tuna £1.12 11')+'n') ##adds a new line into text file
skittle = channel.write(('71616799 Skittles £2.14 17')+'n') ##adds a new line into text file
bar = channel.write(('48156322 Bar of Chocolate £0.99 24')+'n') ##adds a new line into text file
channel.close() ##closes the writing text file

channel=open('List.txt','r') ##reads a set up text file in neat
for line in channel: ##
print(line) ##prints out the text file line by line
channel.close() ##

while valid==False: ##starts a loop including all below
valid=True ##sets valid true to start loop

print("   ") ##
print("Type the Gtin of what you would like to buy below...") ##asks the user what they want to buy from the list
print("   ") ##
want = input("What item would you like to purchase: ") ##lets the user input what they want to buy
print("   ") ##

if (want == "82571465") or (want == "28528243") or (want == "71616799") or (want == "48156322"): ##if input doesnt equal one of these on the list it automatically restarts the loop

    if want=="82571465": ##looks if the input was equal to this
        print(beanstock," cans of beans in stock...") ##print amount of stock stored
        beans1 = int(input("How many Can of Beans would you like to buy: ")) ##asks user to input how many they want to buy
        if 1 <= beans1 <= beanstock: ##checks if input is in range of stock
            print ("Added") ##
            print("  ") ##
            beantotal1 = (0.86*beans1)##calculates how much they have to pay for the amount they want by the price
            print(round(beantotal1,2)) ##prints how much it costs to 2 decimal places
            round(beantotal1,2) ##rounds amount to store for final bill
            beanstock = (beanstock-beans1) ## takes the amount user wants from the total stock
        else: ##if it the input isnt in range of stock it prints this out
            print("We currently don't have that many in stock, please try again...") ##
            valid=False ##restarts the loop if not in range of stock

    if want=="28528243": ##looks if the input was equal to this
        print(tunastock," tins of tuna in stock...") ##prints amount of stock stored
        tuna1 = int(input("How many Tins of tuna would you like to buy: ")) ##asks user to input how many they want to buy
        if 1 <= tuna1 <= tunastock: ## checks if input is in range of stock
            print(tuna1," Added to shopping list") ##
            print("   ") ##
            tunatotal1= (1.12*tuna1) ##calculates how much they have to pay for the amount they want by the price
            print(round(tunatotal1,2)) ##prints how much it costs to 2 decimal places
            round(tuna1,2) ##rounds amount to store for the final bill
            tunastock = (tunastock-tuna1) ## takes the amount user wants from the total stock
        else: ##if input isnt in range of stock this is printed out
            print("We currently don't have that many in stock, please try again...") ##
            valid=False ##restarts the loop if not in range of stock

    if want=="71616799": ##looks if the input was equal to this
        print(skittlestock," bags of skittles in stock...") ##prints amount of stock stored
        skittle1 = int(input("How many Packs of Skittles would you like to buy: ")) ##asks user to input how many they want
        if 1 <= skittle1 <= skittlestock: ## checks if the input is in range of stock
            print(skittle1," Added to shopping list") ##
            print("   ") ##
            skittletotal1 = (2.14*skittle1) ##calculates how much the user has to pay for the amount they want by the price
            print(round(skittletotal1,2)) ## prints how much it costs to 2 decimal places
            round(skittle1,2) ##rounds amount to store the final bill
            skittlestock = (skittlestock-skittle1) ##takes the amount the user wants from the total stock
        else: ##if the user input is not in range of stock this is printed out
            print("We currently don't have that many in stock, please try again...") ##
            valid=False ##restarts loop if not in range of stock

    if want=="48156322": ##looks if the input was equal to this
        print(barstock," bars of chocolate in stock...") ##prints amount of stock stored
        bar1 = int(input("How many Bars of Chocolate would you like to buy: ")) ##asks user to input how many they want
        if 1 <= bar1 <= barstock: ## checks if the input is in range of stock
            print(bar1," Added to shopping list") ##
            print("   ") ##
            bartotal1 = (0.99*bar1) ##calculates how much the user has to pay for the amount they want by the price
            print(round(bartotal1,2)) ## prints how much it costs to 2 decimal places
            round(bar1,2) ##rounds amount to store the final bill
            barstock = (barstock-bar1) ##takes the amount the user wants from the total stock
        else: ##if the user input is not in range of stock this is printed out
            print("We currently don't have that many in stock, please try again...") ##
            valid=False ##restarts loop if not in range of stock

    yesno = input("Would you like anything else? (yes/no): ") ##asks the user if they want to buy anything else after each of the products listed

    if (yesno == "no") or (yesno=="No"): ##checks if the user does want to buy something else, if no...
        finalbill = float(bartotal1) + float(skittletotal1) + float(beantotal1) + float(tunatotal1) ##the final bill is stored
        print(beans1," Cans of Beans") ##prints out how many cans of beans they wanted to buy
        print(tuna1," Tins of Tuna") ##prints out how many tins of tuna they wanted to buy
        print(skittle1," Bags of Skittles") ##prints out how many bags of skittles they wanted to buy
        print(bar1," Bars of Chocolate") ##prins out how many bars of chocolate they wanted to buy
        print("** ",beans1 + tuna1 + skittle1 + bar1," items bought in total  **") ##prints the total amount of items they purchased
        print("Your final bill is: ") ##
        print(round(finalbill,2))##prints out the total amount of money they have to pay for the items they purchased to 2 decimal places

        channel=open('List1.txt','w')


        valid=True ##ends program
    else: ##if they want to buy something else it sends them back to the stored items for them to purchase more and stores what they have already added to their shopping list
        valid=False ##goes back to the stock

else: ##
    quit()## if no gtin from the stocked items is typed in it exits the program for them to open up and restart