adding mushrooms sorrywe are out of green peppers right now adding extra cheese finished making your pizzachecking that list is not empty we've made simple assumption about every list we've worked with so farwe've assumed that each list has at least one item in it soon we'll let users provide the information that' stored in listso we won' be able to assume that list has any items in it each time loop is run in this situationit' useful to check whether list is empty before running for loop as an examplelet' check whether the list of requested toppings is empty before building the pizza if the list is emptywe'll prompt the user and make sure they want plain pizza if the list is not emptywe'll build the pizza just as we did in the previous examplesu requested_toppings [ if requested_toppingsfor requested_topping in requested_toppingsprint("adding requested_topping "print("\nfinished making your pizza!" elseprint("are you sure you want plain pizza?"this time we start out with an empty list of requested toppings at instead of jumping right into for loopwe do quick check at when the name of list is used in an if statementpython returns true if the list contains at least one iteman empty list evaluates to false if requested_toppings passes the conditional testwe run the same for loop we used in the previous example if the conditional test failswe print message asking the customer if they really want plain pizza with no toppings the list is empty in this caseso the output asks if the user really wants plain pizzaare you sure you want plain pizzaif the list is not emptythe output will show each requested topping being added to the pizza if statements