[Python-ideas] Improving Catching Exceptions

[Cameron Simpson]

On 22Jun2017 19:47, Andy Dirnberger <dirn at dirnonline.com> wrote:
>> On Jun 22, 2017, at 7:29 PM, Cameron Simpson <cs at zip.com.au> wrote:
>>   try:
>>       foo(bah[5])
>>   except IndexError as e:
>>       ... infer that there is no bah[5] ...
>>
>> Of course, it is possible that bah[5] existed and that foo() raised an IndexError of its own. One might intend some sane handling of a missing bah[5] but instead silently conceal the IndexError from foo() by mishandling it as a missing bah[5].
>>
>> Naturally one can rearrange this code to call foo() outside that try/except, but that degree of control often leads to quite fiddly looking code with the core flow obscured by many tiny try/excepts.
[...]
>
>How about something like this?
>
>    try:
>        val = bah[5]
>    except IndexError:
>        # handle your expected exception here
>    else:
>        foo(val)

That is the kind of refactor to which I alluded in the paragraph above.  Doing 
that a lot tends to obscure the core logic of the code, hence the desire for 
something more succinct requiring less internal code fiddling.

Cheers,
Cameron Simpson <cs at zip.com.au>