You shouldn’t need to define the columns. Here’s another test script:
###########################
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()
engine = sa.create_engine('sqlite:///hybridtest.db')
engine.execute("""
CREATE TABLE sample (
pk INTEGER NOT NULL,
nsa_mstar FLOAT,
PRIMARY KEY (pk)
)
""")
class Sample(Base):
__tablename__ = 'sample'
__table_args__ = {'autoload' : True, 'autoload_with': engine}
@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)
###########################
What database are you using, and what is your SQL table definition? Does your
table already have a nsa_logmstar column? (I don’t think that should matter,
but it would be worth checking)
Simon
> On 15 Jan 2016, at 22:27, Brian Cherinka <havok2...@gmail.com> wrote:
>
> It looks like I needed to define the columns inside my class. That's the
> only difference between your class and mine. And I tested out the query and
> it now works, and returns the correct number of rows.
>
> In [4]: print
> session.query(datadb.Sample.pk).filter(datadb.Sample.nsa_logmstar < 9)
>
> SELECT datadb.sample.pk AS datadb_sample_pk
> FROM datadb.sample
> WHERE log(datadb.sample.nsa_mstar) < %(log_1)s
>
> In [6]: len(session.query(datadb.Sample.pk).filter(datadb.Sample.nsa_logmstar
> < 9,datadb.Sample.nsa_mstar > 0).all())
> Out[6]: 273
>
> Do you have any idea why the column definition matters here? Thanks for all
> your help.
>
> Brian
>
> On Friday, January 15, 2016 at 5:02:03 PM UTC-5, Brian Cherinka wrote:
> 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> 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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