Storm

Storm is the ORM from Canonical (makers of Ubuntu.) Here is the simple implementation I have that utilizes CP 3.1 (Currently Beta) and Storms current trunk release (.11 i believe it is).

Modifications:

 * 2009-05-20: Nando Florestan corrected to_skip exceptions.
 * 2007-11-20: Updated connect_db, and disconnect_db methods to remove stores when thread has died.

For my connection setup, here is the code.
{{{
storm_stores = {}

def connect_db(thread_index):
	global storm_stores
	database = create_database(cherrypy.config.get('storm.default.url'))
	local_store		= Store(database)
	storm_stores[thread_index] = local_store
	cherrypy.thread_data.store = local_store
	
def disconnect_db(thread_index):
	global storm_stores
	s = storm_stores.pop(thread_index, None)
	if s is not None:
		cherrypy.log("Cleaning up store.", "STORM")
		s.close()
	else:
		cherrypy.log("Could not find store.", "STORM")

	
cherrypy.engine.subscribe('start_thread', connect_db)
cherrypy.engine.subscribe('stop_thread', disconnect_db)
}}}

In your config file you will want:
{{{
storm.default.url = "postgres://postgres:pass@server:5432/database"
}}}

Here is a sample method that uses genshi, storm etc:
{{{
@cherrypy.expose
@template.output('index.html')
def index(self, site_id=1):
    site = cherrypy.thread_data.store.find(Site, Site.site_id == 1).one()
    cherrypy.thread_data.store.commit() # necessary unless you use the tool provided below.
    return template.render(site=site)
}}}

Instead of doing a commit on every query in every action you can allow the request handler to do the commit for you. This is very similar to the [http://tools.cherrypy.org/wiki/Dejavu Dejavu] example shown in the tools section as well. This basically attempts to do a commit and if it doesn't commit it does a rollback and spits out an error.

{{{
## The database commit tool. This will try to auto-commit on each request.
def do_commit():
	try:
		if not cherrypy.request.rolledback:
			cherrypy.thread_data.store.commit()
	except:
		cherrypy.thread_data.store.rollback()
		cherrypy.log("ROLLBACK - " + format_exc(), "STORM")
		

def try_commit():
	if cherrypy.response.stream:
		cherrypy.request.hooks.attach('on_end_request', do_commit)
	else:
		if isinstance(cherrypy.response.body, types.GeneratorType):
			cherrypy.response.collapse_body()
		do_commit()

class StormHandlerWrapper(object):
	# to_skip = (KeyboardInterrupt, SystemExit, cherrypy.HTTPRedirect)
	# Nando Florestan does not think the above line is correct,
	# because transactions should never be interrupted in the middle:
	to_skip = [cherrypy.HTTPRedirect]
	
	def __init__(self):
		self.nexthandler = cherrypy.request.handler
		cherrypy.request.handler = self

	def __call__(self, *args, **kwargs):
		try:
			cherrypy.request.rolledback = False
			result = self.nexthandler(*args, **kwargs)		
		except Exception, e:
			if not isinstance(e, self.to_skip):
				cherrypy.log("ROLLBACK - " + format_exc(), "STORM")
				cherrypy.thread_data.store.rollback()
				cherrypy.request.rolledback = True
			raise
		return result

class StormTool(cherrypy.Tool)	:
	def _setup(self):
		cherrypy.request.hooks.attach('before_handler', StormHandlerWrapper, priority=100)
		cherrypy.Tool._setup(self)

cherrypy.tools.storm = StormTool('on_end_resource', try_commit)
}}}

Simply create the tool and  then in your config you need to have

{{{

tools.storm.on = True
}}}

If you have questions I go by Zenom on the #cherrypy channel.  A big thanks goes out to fumanchu_, mcella, Niemeyer (Storm) and Radix (Storm) for all their help in getting this working.