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I wrote a program that receives from the user one string representing a shopping list. The program asks the user to enter a number between 1 and 9. Depending on the number received, do one of the following: And after making a user selection, the user returns to the main menu until they select number 9 to exit. The syntax is correct but the program does not print what is needed. How to fix it?

def shopping_list(my_str):
    my_list = my_str.split(",")
    i = input("Please choose a number between 1 and 9: ")
    while i in range(1, 10):
        if i == 1:
            print("My shopping list:", my_list)
            continue
        elif i == 2:
            print("The number of items in my shopping list:", len(my_list))
            continue
        elif i == 3:
            product = input("Please enter a product name: ")
            if product in my_list:
                print("This product is in the shopping list.")
            else:
                print("This item is not in the shopping list.")
            continue
        elif i == 4:
            product = input("Please enter a product name: ")
            print("The item", product, "shows", my_list.count(product), "in the list")
            continue
        elif i == 5:
            product = input("Please enter a product name: ")
            new_list = my_list.remove(product)
            print("The item", product, "remove from the list. The new list is", new_list)
            continue
        elif i == 6:
            product = input("Please enter a product name: ")
            my_list += product
            print("The item", product, " add to the list. The new list is", my_list)
            continue
        elif i == 7:
            new_list = []
            for product in my_list:
                if len(product) < 3 or not(product.isalpha()):
                    new_list += product
            continue
        elif i == 8:
            print(list(set(my_list)))
            continue
        else:
            break
shopping_list("Milk,Cottage,Tomatoes")
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  • 1
    Look at where you are taking in user input. Commented May 13, 2020 at 21:17
  • i never changes inside the loop, so that's an infinite loop Commented May 13, 2020 at 21:17
  • Use continue when you want to avoid code that comes next, here there is just elif so no other code will be executed : remove all the continue statement Commented May 13, 2020 at 21:19
  • input() returns a string value, and therefore while i in range(1, 10) will never execute. Commented May 13, 2020 at 21:20
  • replace your input() inside your loop to reiterate the request with while true. Commented May 13, 2020 at 21:22

2 Answers 2

Reset to default
1
  • You never ask again the user, so the loop goes infite doing the first choice given by the user.
  • Also remove the continue statement, you don't need them as all code is in elif also it'll allow you to ask the user a new choice at the end of the loop.
  • convert the input to int, you won't be able to enter the loop without
def shopping_list(my_str):
    my_list = my_str.split(",")
    i = int(input("Please choose a number between 1 and 9: "))
    while i in range(1, 10):
        if i == 1:
            print("My shopping list:", my_list)                
        elif i == 2:
            print("The number of items in my shopping list:", len(my_list))
        elif i == 3:
        # ...
        elif i == 8:
            print(list(set(my_list)))
        else:
            break
        i = int(input("Please choose a number between 1 and 9: "))

Final Full Code

Now corrections about

  • mode 5 : what is returned by remove is None, the modification is in-placed so do 

    elif i == 5:
    product = input("Please enter a product name: ")
    my_list.remove(product)
    print("The item", product, "remove from the list. The new list is", my_list)

  • mode 6 the operator += does an extend on the list so it'll add all chars, do append instead

    elif i == 6:
    product = input("Please enter a product name: ")
    my_list.append(product)
    print("The item", product, " add to the list. The new list is", my_list)

  • mode 7 creating a new list that is a filter of the main one is useless if you forget it. Also I'd say you remove the items that are smaller than 3 or contains non-alpha, here you keep them. Finally use append

    elif i == 7:
    new_list = []
    for product in my_list:
        if len(product) >= 3 and product.isalpha():
            new_list.append(product)
    my_list = list(new_list)

    or just use a list comprehension

    elif i == 7:
    my_list = [p for p in my_list if len(p) >= 3 and p.isalpha()]
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4 Comments

@JohnGordon thanks, I was preparing the fix of the list error too
@Shlomit did you accept the answer that explains just 25% of the problems ?
@JohnGordon thank you so much, it was very helpful! Why when i == 5 can't I add an item that already exists in the list? Why when i == 8 and the same item appears about 3 times does it not make it distinct and returns it twice? set Shouldn't remove duplicates?
@Shlomit Me is azro ^^ you should type them exactly the same , now why did you accept the other answer that does not tell you about your other problems ?
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I would do this: (Cut out some elifs due to too much code.)


while True:
    i = int(input("Please choose a number between 1 and 9: "))

    if i == 1:
            print("My shopping list:", my_list)
            continue
        elif i == 8:
            print(list(set(my_list)))
            continue
        elif i == 9:
            break
        else:
            print("Invalid Number! Try again.")

Is this what you want? I'm not quite getting what you're asking for.

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