[Python-Dev] Fwd: Change in repr of Decimal in 2.6

[Karen Tracey]

Meant to copy list on reply, sorry.

---------- Forwarded message ----------
From: Karen Tracey <kmtracey at gmail.com>
Date: Fri, Jul 18, 2008 at 11:48 PM
Subject: Re: [Python-Dev] Change in repr of Decimal in 2.6
To: Raymond Hettinger <python at rcn.com>


On Fri, Jul 18, 2008 at 11:19 PM, Raymond Hettinger <python at rcn.com> wrote:

> From: Karen Tracey
>
>> I noticed when trying out Python's 2.6b2 release that the repr of Decimal
>> has changed since 2.5.  On 2.5:
>>
> ...
>
>>  quotes were used whereas on 2.6b2:
>>
> ...
>
>> single quotes are used.  Searching around I see this was done in r60773
>> with the log message:
>> Fix decimal repr which should have used single quotes like other reprs.
>>
>> but I can't find any discussion other than that.
>>
>
> Guido requested this change so that the Decimal repr would match the style
> used elsewhere (i.e. str(7) --> '7').
>

Thanks for the background.  Can't say I ever noticed the inconsistency
myself.


>
>  If it's here to stay, is there some straightforward way that I am unaware
>> of to construct tests that use Decimal repr but will work correctly on
>> Python 2.3-2.6?
>>
>
> A quick hack is to monkey patch the decimal module:
>
>   >>> import decimal
>   >>> decimal.Decimal.__repr__ = lambda s: 'Decimal("%s")' % str(s)
>

That is quick, but does seem hackish.


> A better fix is to amend to doctests to not rely on the __repr__ format.
> Instead of:
>
>  >>> Decimal('7.1')
>  Decimal("7.1")
>
> use:
>
>  >>> print Decimal('7.1')
>  7.1
>

Yeah, but the testcases are not quite that simple.  They're often testing
return values from functions and as much verifying that the type is correct
as the value, so I think I'd have to change stuff like:

>>> f.clean('1')
Decimal("1")

to:

>>> x = f.clean('1')
>>> print type(x), x
<class 'decimal.Decimal'> 1

right?

Thanks for the answer,
Karen
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