Re: DecimalField Problem

On Wed, 8 Jan 2014 16:44:56 +0100, Erik Cederstrand
<erik+lists@cederstrand.dk> declaimed the following:

>Den 08/01/2014 kl. 16.18 skrev Timothy W. Cook <tim@mlhim.org>:
>
>> I have several decimal fields defined in the model like this:
>>
>> min_inclusive = models.DecimalField(_('minimum inclusive'), max_digits=19, decimal_places=10, help_text=_("Enter the minimum (inclusive) value for this concept."), null=True, blank=True)
>>
>> Via the admin interface when I enter a 0 (zero) and save the object I get 0E-10 as the value. I am using PostgreSQL 9.1 for persistence.
>>
>> So, why doesn't it just store a zero?
>
>Underneath a DecimalField there is a Python float type, and some equivalent float type in your database. Float values are an approximation, so 0.000000000000 and 0 are not guaranteed to be equal. See http://stackoverflow.com/questions/2986150/python-floating-number
>
If Django's "DecimalField" is NOT use Python's Decimal type, I'd be
concerned... Python's Decimal is NOT a "float".

However, the conversion of a Decimal to/from PostgreSQL might result in
a floating point value -- which I'd consider a flaw in the database adapter
as PostgreSQL does have a NUMERIC data type that should map directly to
Python Decimal.
--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com HTTP://wlfraed.home.netcom.com/

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