[Python-Dev] PEP 409 and the stdlib

[Serhiy Storchaka]

21.05.13 13:05, Hrvoje Niksic написав(ла):
> On 05/21/2013 11:56 AM, Serhiy Storchaka wrote:
>> try:
>>       x = d['key']
>> except KeyError:
>>       x = fallback('key')
>>
>> def fallback(key):
>>       if key not in a:
>>           raise BusinessError(...)
>>       return 1 / a[key] # possible TypeError, ZeroDivisionError, etc
>
> Yes, in that case the exception will appear unintentional and you get
> the old message — it's on a best-effort basis.

In both cases the BusinessError exception raised explicitly. How do you 
distinguish one case from another?