How to check user input (Python)

debugcn Published at Dev

Ryan

I have seen many answers to this question but am looking for something very specific. What I need to accomplish (in pseudo code) is this:

> FOR every ITEM in DICTIONARY, DO:
>           PROMPT user for input
>           IF input is integer
>                 SET unique-variable to user input

I'm very new to Python so the code may not be proper, but here is what I have:

def enter_quantity():
  for q in menu:
      quantities[q] = int(input("How many orders of " + str(q) + "?: "))

So this does everything but evaluate the user input. The problem I'm having is if the input is incorrect, I need to re-prompt them for the same item in the top-level for loop. So if it's asking "How many slices of pizza?" and the user inputs "ten", I want it to say "Sorry that's not a number" and return to the prompt again of "How many slices of pizza?".

Any/all ideas are appreciated. Thanks!

My final solution:

def enter_quantity():
for q in menu:
    booltest = False
    while booltest == False:
        inp = input("How many orders of " + str(q) + "?: ")
        try:
            int(inp)
            booltest = True
        except ValueError:
            print (inp + " is not a number. Please enter a nermic quantity.")
    quantities[q] = int(inp)

Padraic Cunningham

You need a while loop with a try/except to verify the input:

def enter_quantity():
    for q in menu:
        while True:
            inp = input("How many orders of {} ?: ".format(q))
            try:
               inp = int(inp) # try cast to int
               break
            except ValueError:
                # if we get here user entered invalid input so print message and ask again
                print("{} is not a number".format(inp))
                continue
        # out of while so inp is good, update dict
        quantities[q] = inp

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