yes, looking at psycopg2's source code i can see that its checking
for python 2.4 and then using Decimal:
if sys.version_info[0] >= 2 and sys.version_info[1] >= 4:
define_macros.append(('HAVE_DECIMAL','1'))
#ifdef HAVE_DECIMAL
PyObject *decimal = PyImport_ImportModule("decimal");
if (decimal) {
decimalType = PyObject_GetAttrString(decimal, "Decimal");
}
#endif
So, I did a test locally with PG and confirmed that you do in fact
get a Decimal back when using Py2.4:
db = create_engine('postgres://scott:[EMAIL PROTECTED]/test?echo=True')
table = Table('sometable', db,
Column('col1', Numeric))
db.create(table)
db.execute(table.insert(), dict(col1=2.5))
x = db.connect().scalar(table.select())
print type(x)
print x
<class 'decimal.Decimal'>
2.50
The Numeric types in SQLAlchemy dont modify the incoming or outgoing
return type of bind parameters at all. this disagrees with your
initial assertion that you get a "float" type back....so...do you
have a test case ? is it possible you are assigning a "float" to a
mapped object and then just getting back that same float without any
DB round trip going on ?
On Jun 3, 2006, at 3:42 AM, Yuan HOng wrote:
> Thanks for pointing this out. I found out that psycopg 1.1.21 gives
> back a Numeric as float. When I switched to psycopg2, a Decimal object
> is automatically returned.
>
> I was switching from SQLObjects, and there the Numeric is
> automatically converted to Decimal seemingly by SQLObjects, so I took
> that for granted. Maybe this should also be added to SA, since then
> the application won't be dependant on the return type of the DBAPI
> layer?
>
> On 6/3/06, Michael Bayer <[EMAIL PROTECTED]> wrote:
>> the float type coming from Numeric etc. is straight from the DBAPI,
>> in this case psycopg2. If youd like to make your own Decimal type
>> which translates this value back and forth from whatever float value
>> psycopg2 is giving you, simply subclass TypeDecorator, specify
>> Numeric as the 'impl', and implement the appropriate
>> convert_bind_param(), convert_result_value() methods.
>>
>> instructions are here:
>>
>> http://www.sqlalchemy.org/docs/types.myt#types_custom
>>
>> if you get that done, theres no reason it cant be stuck into the
>> types module, just wouldnt be available if youre on 2.3.
>>
> --
> Hong Yuan
>
> 大管家网上建材超市
> 装修装潢建材一站式购物
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