[Python-Dev] PEP 409 and the stdlib

[Ethan Furman]

On 05/20/2013 11:32 AM, Terry Jan Reedy wrote:
> On 5/20/2013 11:39 AM, Steven D'Aprano wrote:
>> On 21/05/13 00:12, Ethan Furman wrote:
>>
>>
>>> As a case in point, base64.py is currently getting a bug fix, and also
>>> contains this code:
>>>
>>> def b32decode(s, casefold=False, map01=None):
>>>      .
>>>      .
>>>      .
>>>      for i in range(0, len(s), 8):
>>>          quanta = s[i: i + 8]
>>>          acc = 0
>>>          try:
>>>              for c in quanta:
>>>                  acc = (acc << 5) + b32rev[c]
>>>          except KeyError:
>>>              raise binascii.Error('Non-base32 digit found')
>>>      .
>>>      .
>>>      .
>>>          else:
>>>              raise binascii.Error('Incorrect padding')
>>>
>>> Does the KeyError qualify as irrelevant noise?
>>
>>
>> IMO, it is irrelevant noise, and obviously so. The binascii.Error raised
>> is not a bug to be fixed, it is a deliberate exception and part of the
>> API of the binascii module. That it occurs inside an "except KeyError"
>> block is a mere implementation detail.
>
> Yes, the code could be revised to make a check on c before the indexing.
> This would be redundant (and a slowdown) in that the check is already done by the indexing mechanism. The whole point of
> the above is to *replace* the default KeyError with a custom binascii.Error for too-large chars.
>
> And I agree with Georg, please say which bad digit was found.

Actually, that was Antoine, but I'm sure Georg also agrees.  ;)

--
~Ethan~