class CachedSingleton(object):
"""Provides caching singleton storage for data access decoration.
Usage:
class CachedSingletonClass(CachedSingleton):
def _getitem(self, name):
# implement data getting routine, such as db access
CachedSingletonClass().attribute1 # returns value as if _getitem('attribute1') was called
CachedSingletonClass().attribute2 # returns value as if _getitem('attribute2') was called
CachedSingletonClass().__doc__ # returns real docstring
"""
__instance = None
def __new__(classtype, *args, **kwargs):
if classtype != type(classtype.__instance):
classtype.__instance = object.__new__(classtype, *args, **kwargs)
classtype.__instance.cache = {}
return classtype.__instance
# to be implemented by contract in the descendant classes
def _getitem(self, name):
return None
def __getattribute__(self, name):
try:
return object.__getattribute__(self, name)
except:
if not self.cache.has_key(name):
self.cache[name] = self._getitem(name)
return self.cache[name]
