for validation/mutation of incoming data you'd normally use the @validates decorator or set up a listener event:
http://www.sqlalchemy.org/docs/orm/mapper_config.html#simple-validators http://www.sqlalchemy.org/docs/orm/events.html#sqlalchemy.orm.events.AttributeEvents to mutate returned data on the "read" side, you need to wrap around the mapped attribute. The most flexible way to do this is with the hybrid system, since it gives you control over the data side and the query side, and optionally lets you modify the write side as well not unlike how the validators work, except using plain descriptors: from sqlalchemy.ext.hybrid import hybrid_property class MyClass(Base): # ... _name = Column('name', String) @hybrid_property def name(self): return "my name is:" + self._name Hybrids are introduced at http://www.sqlalchemy.org/docs/orm/extensions/hybrid.html . if you don't like typing "name" so much it can be automated using a recipe I just made up at http://www.sqlalchemy.org/trac/wiki/UsageRecipes/QuickHybrid , it would look like this: class MyClass(Base): __tablename__ = 'mytable' id = Column(Integer, primary_key=True) @mapped_column(String) def _name(self, value): return "The name is: " + value the recipe maintains all the same capabilities as a hybrid with a separate column, just uses some mild trickery to combine the two steps. On Oct 11, 2011, at 4:47 PM, Nathan Rice wrote: > I need to add some processing to mapped attributes. For instance, > some extra client side validation, returning attribute values embedded > in markup, etc. > > Is there a better way to do this than to change the column definition > (i.e. Column(name, type_, key="_name")) and adding a descriptor to the > class' name attribute which then writes to _name? > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To post to this group, send email to sqlalchemy@googlegroups.com. > To unsubscribe from this group, send email to > sqlalchemy+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/sqlalchemy?hl=en. > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
