我一直在尝试了解 python 弱引用列表/字典的工作原理.我已经阅读了它的文档,但是我无法弄清楚它们是如何工作的,以及它们的用途.谁能给我一个他们所做工作的基本示例以及他们如何工作的解释?
I have been trying to understand how python weak reference lists/dictionaries work. I've read the documentation for it, however I cannot figure out how they work, and what they can be used for. Could anyone give me a basic example of what they do and an explanation of how they work?
(EDIT) 使用 Thomas 的代码,当我用 obj 替换 [1,2,3] 它抛出:
(EDIT) Using Thomas's code, when i substitute obj for [1,2,3] it throws:
Traceback (most recent call last): File "C:/Users/nonya/Desktop/test.py", line 9, in <module> r = weakref.ref(obj) TypeError: cannot create weak reference to 'list' object 推荐答案理论
引用计数通常是这样工作的:每次创建对对象的引用时,它都会加一,每当删除一个引用时,它就会减一.
Theory
The reference count usually works as such: each time you create a reference to an object, it is increased by one, and whenever you delete a reference, it is decreased by one.
弱引用允许您创建对不会增加引用计数的对象的引用.
Weak references allow you to create references to an object that will not increase the reference count.
python 的垃圾收集器在运行时使用引用计数:任何引用计数为 0 的对象都将被垃圾收集.
The reference count is used by python's Garbage Collector when it runs: any object whose reference count is 0 will be garbage collected.
你会为昂贵的对象使用弱引用,或者避免循环引用(尽管垃圾收集器通常自己做).
You would use weak references for expensive objects, or to avoid circle references (although the garbage collector usually does it on its own).
这是一个演示其用法的工作示例:
Here's a working example demonstrating their usage:
import weakref import gc class MyObject(object): def my_method(self): print 'my_method was called!' obj = MyObject() r = weakref.ref(obj) gc.collect() assert r() is obj #r() allows you to access the object referenced: it's there. obj = 1 #Let's change what obj references to gc.collect() assert r() is None #There is no object left: it was gc'ed.更多推荐
python中的弱引用
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