看着django.utils.functional我注意到一个LazyObject类，django 使用它django.conf：
class LazySettings(LazyObject):
它是 的定义LazyObject：
class LazyObject(object):
"""
A wrapper for another class that can be used to delay instantiation of the
wrapped class.
By subclassing, you have the opportunity to intercept and alter the
instantiation. If you don't need to do that, use SimpleLazyObject.
"""
def __init__(self):
self._wrapped = None
def __getattr__(self, name):
if self._wrapped is None:
self._setup()
return getattr(self._wrapped, name)
def __setattr__(self, name, value):
if name == "_wrapped":
# Assign to __dict__ to avoid infinite __setattr__ loops.
self.__dict__["_wrapped"] = value
else:
if self._wrapped is None:
self._setup()
setattr(self._wrapped, name, value)
def __delattr__(self, name):
if name == "_wrapped":
raise TypeError("can't delete _wrapped.")
if self._wrapped is None:
self._setup()
delattr(self._wrapped, name)
def _setup(self):
"""
Must be implemented by subclasses to initialise the wrapped object.
"""
raise NotImplementedError
# introspection support:
__members__ = property(lambda self: self.__dir__())
def __dir__(self):
if self._wrapped is None:
self._setup()
return dir(self._wrapped)
我想知道使用的最佳情况是LazyObject什么？