[Tutor] Exception not working as expected?

[Cameron Simpson]

On 02Mar2019 00:05, Alan Gauld <alan.gauld at yahoo.co.uk> wrote:
>On 01/03/2019 19:23, Chip Wachob wrote:
>> I'm not sure what you mean by putting the except close to the int().
>
>He means you should have a try/except for the int conversion,
>typically something like:
>
>
>  # wait for it...
>  try: num_items = int(raw_input(": "))
>  except ValueError:
>     # try a second time.
>
>  if num_items == 0: # individual testing
>     print "\nIndividual testing requested"
>
>That means the user has a chance of continuing without errors
>and you don;t need to use recursion to restart the menu system.

Just further to this remark of Alan's: you should make try/except 
clauses as small as is reasonable i.e. containing as little code as 
possible between "try" and "except".

Not only does this have the advantage Alan mentioned, of making it 
possible to offset the user the chance to continue after an error, it 
_also_ means you have more confidence about what caused the exception.

In you programme, you have a try/except around the entire main body of 
your loop. This means that the "except ValueError" clause will intercept 
_any_ ValueError issued by the code, not just the one from the int() 
call, so it needn't indicate bad user input, it could as easily indicate 
some subsequent bug in your code, as many functions can raise ValueError 
if they are handed something unsatisfactory.

Cheers,
Cameron Simpson <cs at cskk.id.au>