Google app engine: pass Model name as a parameter to a function

Question

To reduce datastore reading and writing, people suggest using memcache:

Write:

entity.put()
memcache.set(entity.key.id(), entity)

Read:

# id known:
entity = memcache.get(id)
if entity is None:
    entity = Model.get_by_id(id)
    memcache.set(id, entity)

I'd like to implement the above as two functions:

def memPut(entity):
    entity.put()
    memcache.set(entity.key.id(), entity)

def memGet(Model, id):
    entity = memcache.get(id)
    if entity is None:
        entity = Model.get_by_id(id)
        memcache.set(id, entity)

memGet is just hypothetical. My questions: 1) how do I pass the name of the Model to the function as an parameter? 2) If an entity is created without specifying an id, GAE will use an integer as its id. What if there are two entities (of course from different models) having the same id? Would memcache.get(id) work?

ewestern ewestern · Accepted Answer · 2013-03-01T13:21:47

If you want the same functions available for all entity types, one simple option would be to subclass all your models from a parent model, which implements the following class methods:

class ParentClass(db.Model):
    @classmethod
    def memPut(cls, entity):
        entity.put()
        memcache.set(entity.key().id(), entity)

    @classmethod
    def memGet(cls, id):
        entity = memcache.get(id)
        if entity is None:
             entity = cls.get_by_id(id)
             memcache.set(id, entity)
        return entity

Then, in your handler:

 MyModel.memPut(entity)
 entity = MyModel.memGet(id)

Google app engine: pass Model name as a parameter to a function

2 Answers