为什么weakref 不支持Python 中的内置类型？

Question

In Python weakref document( http://docs.python.org/library/weakref.html ), it says that

Several built-in types such as list and dict do not directly support weak references but can add support through subclassing

I think creating weakref for big dict could be useful in some real cases. I'm wondering what's the reason behind that implementation ?

Answer 1

Most of the built-in types are not directly weak referenceable (eg str, int, float, list, dict, None), and there are a few that cannot even be made so by sub-classing (eg tuples in CPython).

Some details about the underlying implementation of weakrefs for several built-in types can be found in this March-2005 python-list post by Raymond Hettinger .

Answer 2

我有根据的猜测是，内部使用 dicts 和列表来实现弱引用，所以你会在这里遇到鸡蛋鸡的情况。