Actually, the class definition is entirely what I posted in the original
message. I didn't cut anything out of that. I don't define the columns in
mine, as you did. The property nsa_logmstar is not defined anywhere else
in the class or in any other place in this code, or in any code that
interacts with this code.
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)
My database connection is a singleton and my base is defined inside that,
essentially
engine = create_engine(database_connection_string)
Base = declarative_base(bind=engine)
Brian
On Friday, January 15, 2016 at 9:43:39 AM UTC-5, Simon King wrote:
>
> 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 <havo...@gmail.com
> <javascript:>> 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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>>>
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