Here is the print immediately after my original class definition:
print 'sample nsa log mstar', Sample.nsa_logmstar
and the result
sample nsa log mstar None
When I run your script exactly as is, I get the same output as you.
When I replace my class definition with yours, inside my code, as follows
class Sample(Base):
__tablename__ = 'sample'
__table_args__ = {'autoload' : True, 'schema' : 'mangadatadb'} (I
needed to add this line in)
pk = Column(Integer, primary_key=True)
nsa_mstar = Column(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 func.log(cls.nsa_mstar)
now the print statement : print 'sample nsa log mstar', Sample.nsa_logmstar
returns
sample nsa log mstar log(mangadatadb.sample.nsa_mstar)
On Friday, January 15, 2016 at 4:28:31 PM UTC-5, Simon King wrote:
>
> Does my test script produce the right output for you in your installation?
>
> What does the print statement immediately after the class definition
> produce?
>
> Simon
>
> > On 15 Jan 2016, at 19:10, Brian Cherinka <havo...@gmail.com
> <javascript:>> wrote:
> >
> > 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>
> 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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