Django（memcached）不缓存对象

Question

有人能解释一下为什么我要直接从django项目中使用memcached缓存后端？”管理.pyshell“没有返回我的图书对象b，而是没有返回？我的具体步骤是：

In [1]: from django.core.cache import cache

In [2]: key = 1234

In [3]: a = "test value"

In [4]: cache.set(key, a)

In [5]: print cache.get(key)
test value

In [6]: class Book():
   ...:     pages = 100
   ...:     

In [7]: b = Book()

In [8]: b.pages
Out[8]: 100

In [9]: key2 = 4321

In [10]: cache.set(key2, b)

In [11]: print cache.get(key2)
None

谢谢