Redis auto search for python objects
I'm trying to implement classes for which Redis actually holds attributes, but the user of the class is unaware of this (ie. Persistence of objects across multiple clients). I know there are several libraries that port redis to python, but nobody does it just that easily (but please correct me if I'm wrong!)
I have successfully implemented automatic attribute re-storage, but I cannot get the search to work with __getattribute__
without infinite recursion. I think I'm trying to use object.__getattribute__
etc, but obviously I must be missing something:
class redisStored(object):
global redis
# A class method to implement object retrieval from redis
# Call <Classname>.load(<id>) to create a new instance which exists in redis
@classmethod
def load(cls,id):
# Create the object
obj = cls.__new__(cls)
# Set id without calling obj __setattr__
object.__setattr__(obj,'id',int(id))
# Return the object we created
return obj
def __str__(self):
# Return "<ClassName>:<id>" to differentiate ids in redis
# You can use this to say redis.hgetall(g) where g is the instance
return "%s:%s" % (self.__class__.__name__, str(object.__getattribute__(self,'id')))
# self.id here ^ would cause infinite recursion
# This works fine
def __setattr__(self,name,value):
redis.hset(self,name,value)
return object.__setattr__(self,name,value)
# This blows up with infinite recursion, WHY??
def __getattribute__(self,name):
_val = redis.hget(self,name)
if not _val:
return object.__getattribute__(self,name)
else:
return _val
If I trace this, it explodes inside _val = redis.hget(self,name)
, but I can't figure out why. Thanks for any help!
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You have to be very careful when overloading __getattribute__
.
A side effect is that access self.__class__
calls __getattribute__
and creates a bogus redis request.
Since you are using new-style classes, you can use __getattr__
instead and avoid the infinite recursion problem, although if you use __getattr__
, you will return the object's attribute prior to redrawing the value if that attribute already exists in your instance.
Anyway, your object is immutable as long as you overload the method __setattribute__
, so this is not a big problem.
Please refer to this SO answer for more detailed difference between __getattr__
and __getattribute__
: Difference between __getattr__ vs __getattribute__
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