On Aug 10, 2011, at 7:02 AM, Dirk Makowski wrote:
> Hi all,
>
> from a given class I'd like to determine which attributes are columns, not
> only physical columns present in the underlying table, but also those from a
> relationship(). The FAQ seems to provide an answer ("What's the best way to
> figure out which attributes are columns, given a class"), but the proposed
> solution throws an "sqlalchemy.orm.exc.UnmappedClassError: Class
> '<pym.models.usrmgr.Principal object at 0x3a69c10>' is not mapped" error in
> my setup.
>
> I'm using 0.7.2. with declarative classes, e.g.
>
> DbBase = declarative_base()
>
> class Principal(DbBase, PymMixin):
> __tablename__ = "principal"
> __table_args__ = {'schema': 'pym'}
> is_enabled = Column(Boolean, nullable=False, default=False)
> ...
>
> Does is matter that I try to read the attributes from a query?
>
> qry = sess.query(Principal)
> for p in qry:
> print p.display_name
> # Determine columns in last looped entity
> mapper = class_mapper(p) #<---- this throws UnmappedClassError
"p" here is an instance of a Principal, i.e. "p = Principal(x, y, z..)", not a
Principal class. You'd say either class_mapper(type(p)), or object_mapper(p).
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