Mark Dickinson wrote:
> On Tue, Mar 25, 2008 at 9:46 AM, Oleg Broytmann <[EMAIL PROTECTED]> wrote:
>> In 2.5.2 it prints
>>
>> <type 'str'>
>> <type 'unicode'>
>>
>> Why the change? Is it a bug or a feature? Shouldn't .to_eng_string()
>> always return a str?
>
> I'd call this a bug. The change is an accident, a side-effect of the fact
> that in 2.5.1 the coefficient (mantissa) of a Decimal was stored as a
> tuple, and in 2.5.2 it's stored as a string (which greatly improves
> efficiency).
> Clearly in 2.5.2 the mantissa is being stored as a unicode instance in the
> second case; it should be explicitly coerced to str in Decimal.__new__.
>
> If others agree that it's a bug, I'll fix it.
I thought that might be what happened, but I couldn't remember if that
optimisation was a 2.6 only change or not (I suspect it was included in
2.5 as a prereq to the spec compliance updates).
Anyway, +1 on coercing the mantissa to a str() instance in 2.5.
This does raise an interesting point though - currently Decimal in Py3k
is storing the mantissa as a Unicode instance instead of a bytes
instance. The performance implications of that are horrendous since
PyLong_FromUnicode does a malloc, encodes the string into the malloced
buffer, then invokes PyLong_FromString on the result.
To fix this, decimal probably needs to grow something like the following
near the top of the module:
try:
_bytes = bytes
except NameError: # 2.5 or earlier
_bytes = str
and then use _bytes instead of str as appropriate throughout the rest of
the module.
The following is also a problem in Py3k:
>>> from decimal import Decimal as d
>>> d(1)
Decimal('1')
>>> d('1')
Decimal('1')
>>> d(b'1')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/ncoghlan/devel/py3k/Lib/decimal.py", line 659, in __new__
raise TypeError("Cannot convert %r to Decimal" % value)
TypeError: Cannot convert b'1' to Decimal
The isinstance(value, str) check in Py3k is too restrictive - it needs
to accept bytes instances as well.
Cheers,
Nick.
--
Nick Coghlan | [EMAIL PROTECTED] | Brisbane, Australia
---------------------------------------------------------------
http://www.boredomandlaziness.org
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