gistfile1.py

## NOTE: "inspect", "ashint", and calling select([SomeClass]) are
## all SQLAlchemy 0.8 features.  To do this in 0.7 would require more
## internally-dependent code.

from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.compiler import compiles
from sqlalchemy.ext.hybrid import hybrid_property
from sqlalchemy.sql.expression import ColumnElement
from sqlalchemy import inspect

Base = declarative_base()


class NamePathColumn (ColumnElement):
    def __init__(self, entity):
        insp = inspect(entity)
        self.entity = insp.selectable

@compiles(NamePathColumn)
def compile_name_path_column(element, compiler, **kwargs):
    return "%s.node_path" % compiler.process(element.entity, ashint=True)

class Node(Base):
    __tablename__ = 'node'

    id = Column(Integer, primary_key=True)

    @hybrid_property
    def name_path(self):
        raise NotImplementedError("we're just demoing @expression here...")

    @name_path.expression
    def name_path(cls):
        return NamePathColumn(cls)


print select([Node]).where(Node.name_path == 'foobar')

na = aliased(Node)
print select([na]).where(na.name_path == 'foobar')

This is excellent, I was wondering how I could solve the aliased (Node) part. (Typo correction: %s.name_path instead of %s.node_path). Now, I just how to understand it, lol. ;D Thanks!