How can i check if the user has entered a valid value? And how can i then append this value to a list if it was entered correctly?

Question

menu_items = ["French fries", "1/4 pound burger", "1/4 pound chesseburger", "1/2 pound burger", "1/2 pound cheeseburger", "Medium pizza", "Meidum pizza with extra toppings", "Large pizza", "Large pizza with extra toppings", "Garlic bread"]
menu_prices = ["$2.00", "$5.00", "$5.55", "$7.00", "$7.50", "$9.00", "$11.00", "$12.00", "$14.50", "$4.50"]
menu_codes = ["ff", "bb", "ccb", "vb", "vcb", "mp", "mpx", "lp", "lpx", "gb"]

order = input(str("Write the item code of the food you wish to buy: "))
quantity = input(int("How many units of the previous food do want? "))

if order == "ff" or "bb" or "ccb" or "vb" or "vcb" or "mp" or "mpx" or "lp" or "lpx" or "gb":
    print("The item code was inputted correctly")
else:
    print("The item code was inputted incorrectly")

if quantity == (0 < 100):
    print("Quantity entered is inside acceptable range")
else:
    print("Quantity entered is out of range")

This part is the list of the code, it is supposed to be the menu of a restaurant. The user should be able to input only items that are in the list (menu_codes) and any other value entered should be denied. And the quantity should only be between 1-100, and anything different should not be allowed. But for some reason, my "while" loop doesn't work, and it prints always the same thing, here is an example of the output of my code.

Write the item code of the food you wish to buy: this is not on the list
How many units of the previous food do want? 56
The item code was inputted correctly
Quantity entered is out of range

`order == "ff" or "bb"` and so on is interpreted as `(order == "ff") or ("bb")` and `"bb"` always evaluates to `True` so the whole expression is `True`. — Michael Butscher, Oct 01 '18 at 00:42
Regarding `quantity == (0 < 100)` you should read about comparison operators in the Python docs and play around with them a bit in a Python shell — Michael Butscher, Oct 01 '18 at 00:48

score 1 · Answer 1 · answered Oct 01 '18 at 00:53

1

Hope this helps. Quantity should be,

if quantity <= 100:
   print("Quantity entered is inside acceptable range")

answered Oct 01 '18 at 00:53

rodeone2

101
1
5

score 0 · Accepted Answer · answered Oct 01 '18 at 01:04

order = input(str("Write the item code of the food you wish to buy: "))

quantity = input("How many units of the previous food do want::")


if order in menu_codes:
    print("The item code was inputted correctly")
else:
    print("The item code was inputted incorrectly")

if 0 <= int(quantity) <= 100:
    print("Quantity entered is inside acceptable range")
else:
    print("Quantity entered is out of range")

How can i check if the user has entered a valid value? And how can i then append this value to a list if it was entered correctly?

2 Answers2