people will ask for just about anythingespecially when it comes to pizza toppings what if customer actually wants french fries on their pizzayou can use lists and if statements to make sure your input makes sense before you act on it let' watch out for unusual topping requests before we build pizza the following example defines two lists the first is list of available toppings at the pizzeriaand the second is the list of toppings that the user has requested this timeeach item in requested_toppings is checked against the list of available toppings before it' added to the pizzau available_toppings ['mushrooms''olives''green peppers''pepperoni''pineapple''extra cheese' requested_toppings ['mushrooms''french fries''extra cheese' for requested_topping in requested_toppingsx if requested_topping in available_toppingsprint("adding requested_topping " elseprint("sorrywe don' have requested_topping "print("\nfinished making your pizza!"at we define list of available toppings at this pizzeria note that this could be tuple if the pizzeria has stable selection of toppings at vwe make list of toppings that customer has requested note the unusual request'french friesat we loop through the list of requested toppings inside the loopwe first check to see if each requested topping is actually in the list of available toppings if it iswe add that topping to the pizza if the requested topping is not in the list of available toppingsthe else block will run the else block prints message telling the user which toppings are unavailable this code syntax produces cleaninformative outputadding mushrooms sorrywe don' have french fries adding extra cheese finished making your pizzain just few lines of codewe've managed real-world situation pretty effectively