weakref

关于weakref标准库：

>>> help(weakref)

Help on module weakref:

NAME

weakref - Weak reference support for Python.

DESCRIPTION

This module is an implementation of PEP 205:

http://www.python.org/dev/peps/pep-0205/

CLASSES

builtins.object

​ _weakrefset.WeakSet

​ builtins.weakcallableproxy

​ builtins.weakproxy

​ builtins.weakref

​ WeakMethod

​ finalize

collections.abc.MutableMapping(collections.abc.Mapping)

​ WeakKeyDictionary

​ WeakValueDictionary

CallableProxyType = class weakcallableproxy(object)

| Methods defined here:

……

weakref标准库中的弱引用（8.23节）消除了“循环引用数据结构的垃圾回收机制”带来的内存泄露问题。本质来讲，弱引用就是一个对象指针，它不会增加它的引用计数。