SQLAlchemy: How to do Table Reflection and MySQL?

[Prasad, Ramit]

Nick Sabalausky wrote:
> On Mon, 22 Oct 2012 14:35:23 -0700 (PDT)
> darnold <darnold992000 at yahoo.com> wrote:
> >
> > i'm not brave enough to dig too deeply into SQLAlchemy, but maybe this
> > will help? :
> >
> > http://kashififtikhar.blogspot.com/2010/07/using-sqlalchemy-reflection-with-pylons.html
> >
> > that came up from googling "sqlalchemy table reflection tutorial".
> 
> Thanks, your view of Google seems to be far better tailored for Python
> than mine is, that doesn't come up for me anywhere on the first five
> pages of results for that query.
> 
> Unfortunately the info on that page doesn't seem to work for me:
> 
> ----------------------------------
> from sqlalchemy import *
> from sqlalchemy.orm import sessionmaker
> 
> engine = create_engine(my connection string)
> meta = MetaData()
> meta.bind = engine
> meta.reflect()
> 
> Session = sessionmaker(bind=engine)
> session = Session()
> 
> res = session.query(user).filter(user.name=="bert").first()
> print res.name
> ----------------------------------
> 
> That just gives me:
> 
> NameError: name 'user' is not defined
> 
> (And yes, the code given on that page to print out the table info
> *does* indicate a table named 'user' was found.)

This does not seem to be a SQLAlchemy problem. Instead it seems
there is not a variable called `name`. If you define 
the appropriate user it does it work? (From that page it seems 
like user should be a blank class like the following).

class user(object): pass

> 
> I also tried this which also fails:
> 
> res =
> session.query(meta.tables["user"]).filter(meta.tables["user"].name=="bert").first()
> 
> sqlalchemy.exc.ArgumentError: filter() argument must be of type
> sqlalchemy.sql.ClauseElement or string
> 
> The page you linked to appears to get around the matter by manually
> setting up tables filled with the reflected info, but that seems to
> defeat much of the point for me. I may as well just set up the tables
> manually without the reflection, which is what I'll probably do.
> 
> Maybe I just misunderstood what was meant in the SQLAlchemy docs here?:
> 
> "but note that SA can also “import” whole sets of Table objects
> automatically from an existing database (this process is called table
> reflection)."  --
> http://docs.sqlalchemy.org/en/rel_0_7/core/tutorial.html
> 
> It said that but then didn't say how and didn't link to any info on how.

Ramit Prasad



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