What happens if you put the print statement immediately after the class
definition? Is there any chance that you've got "nsa_logmstar = None"
somewhere in your class definition?
Here's a test script which appears to work:
import math
import sqlalchemy as sa
import sqlalchemy.orm as saorm
from sqlalchemy.ext.hybrid import hybrid_property
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class Sample(Base):
__tablename__ = 'sample'
pk = sa.Column(sa.Integer, primary_key=True)
nsa_mstar = sa.Column(sa.Float)
@hybrid_property
def nsa_logmstar(self):
try:
return math.log10(self.nsa_mstar)
except ValueError:
return -9999.0
except TypeError:
return None
@nsa_logmstar.expression
def nsa_logmstar(cls):
return sa.func.log(cls.nsa_mstar)
if __name__ == '__main__':
sm = saorm.sessionmaker()
session = sm()
print session.query(Sample.pk).filter(Sample.nsa_logmstar < 9)
And here's the output:
SELECT sample.pk AS sample_pk
FROM sample
WHERE log(sample.nsa_mstar) < :log_1
Simon
On Fri, Jan 15, 2016 at 2:23 PM, Brian Cherinka <havok2...@gmail.com> wrote:
> Ahh. Thanks. Here is the class side then. Still None.
>
> In [14]: print datadb.Sample.nsa_logmstar
> None
>
> Brian
>
> On Friday, January 15, 2016 at 8:48:30 AM UTC-5, Simon King wrote:
>>
>> "Sample()" is an instance. "Sample" is the class. Try:
>>
>> print datadb.Sample.nsa_logmstar
>>
>> Simon
>>
>> On Fri, Jan 15, 2016 at 1:46 PM, Brian Cherinka <havo...@gmail.com>
>> wrote:
>>
>>> Hi Simon,
>>>
>>> Printing on the class side, I get
>>>
>>> In [11]: print datadb.Sample().nsa_logmstar
>>> None
>>>
>>> It looks like it's getting set to None (or remaining None). I'm not
>>> quite sure what this tells me, except that it's not working. Printing on
>>> in the instance side, I get
>>>
>>> In [12]: print cube.sample[0].nsa_mstar
>>> 1386160000.0
>>>
>>> In [13]: print cube.sample[0].nsa_logmstar
>>> 9.14181336239
>>>
>>> nsa_mstar is a column in my database table, and nsa_logmstar I want to
>>> be simply the log-base10 of that quantity.
>>>
>>> If this doesn't give any insight, then it will take me some time to
>>> provide a small script. This code is embedded into a bunch of stuff. But
>>> I'll work on it.
>>>
>>> Brian
>>>
>>>
>>> On Friday, January 15, 2016 at 5:00:51 AM UTC-5, Simon King wrote:
>>>
>>>> On Fri, Jan 15, 2016 at 6:16 AM, Brian Cherinka <havo...@gmail.com>
>>>> wrote:
>>>>
>>>>> I'm trying to set up a hybrid property / expression in a custom class,
>>>>> that I can use in queries. I think I have the syntax correct, however the
>>>>> query returns the entire table, instead of the correct subset of results.
>>>>> And the where clause just indicates True rather than the correct
>>>>> expression.
>>>>>
>>>>>
>>>>> Here is my hybrid property/expression definition
>>>>>
>>>>> class Sample(Base,ArrayOps):
>>>>> __tablename__ = 'sample'
>>>>> __table_args__ = {'autoload' : True, 'schema' : 'datadb'}
>>>>>
>>>>> def __repr__(self):
>>>>> return '<Sample (pk={0},cube={1})'.format(self.pk,self.cube)
>>>>>
>>>>> @hybrid_property
>>>>> def nsa_logmstar(self):
>>>>> try: return math.log10(self.nsa_mstar)
>>>>> except ValueError as e:
>>>>> return -9999.0
>>>>> except TypeError as e:
>>>>> return None
>>>>>
>>>>> @nsa_logmstar.expression
>>>>> def nsa_logmstar(cls):
>>>>> return func.log(cls.nsa_mstar)
>>>>>
>>>>> The session query is
>>>>>
>>>>> session.query(Sample.pk).filter(Sample.nsa_logmstar < 9)
>>>>>
>>>>> But printing it does not show the appropriate condition. I get
>>>>>
>>>>> SELECT datadb.sample.pk AS datadb_sample_pk,
>>>>> FROM datadb.sample
>>>>> WHERE true
>>>>>
>>>>> and the results return the entire table of ~11000 rows instead of the
>>>>> expected 272 rows. What's going on here? Everything looks correct to me,
>>>>> but I can't figure it out.
>>>>>
>>>>> I'm expecting the SQL statement to look like this
>>>>>
>>>>> select s.pk
>>>>> from datadb.sample as s
>>>>> where log(s.nsa_mstar) < 9;
>>>>>
>>>>> Any thoughts? Thanks.
>>>>>
>>>>>
>>>> I can't see anything obviously wrong with your code, but it looks like
>>>> Sample.nsa_logmstar is not actually resolving to the hybrid property in
>>>> your query. What happens if you "print Sample.nsa_logmstar" just before the
>>>> query?
>>>>
>>>> Otherwise, please provide a small runnable script that demonstrates the
>>>> problem.
>>>>
>>>> Simon
>>>>
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