[Python-Dev] Decimal(unicode)

Tue Mar 25 17:43:10 CET 2008

Facundo Batista wrote:
> 2008年3月25日, Mark Dickinson <dickinsm at gmail.com>:
>>> So int and float accepts bytes, while complex, Decimal and Fraction do
>> not...
>> I'm -1 to accept bytes as input for Decimal, I don't see a case of
> use, and I think that conceptually there's no reason to do it.
>> Of course, I can be wrong, ;)

I was thinking converting directly from bytes would be significantly 
quicker than going through Unicode (e.g. for numbers read from a file), 
but that may not actually be the case (it'll definitely be faster 
because there is less data copying and movement involved, but the speed 
difference may be less dramatic than I first thought). So while the 
internal storage of the mantissa definitely needs to be changed to a 
bytes object in order to retain Mark's hard-won performance 
improvements, the case of whether or not to accept bytes is far less clear.
The way I see it either complex, Decimal and Fraction all need to be 
updated to accept bytes objects, or else int and float need to be 
updated to reject them.
It *definitely* needs to be possible to convert bytes objects to 
integers as if they were ASCII strings - otherwise a lot of wire 
protocol processing would become a nightmare. Indeed, the proposed 
change to Decimal to have it store the mantissa as a bytes object in 
Py3k assumes that it will still be possible to convert that value 
directly to a long object.
Since we have some strong use cases at least for the bytes->int case, 
consistency then suggests that the other numeric types should all accept 
bytes as well (interpreting them as ASCII encoded strings).
Cheers,
Nick.
-- 
Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia
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