Python - 如何使这个不可腌制的对象可腌制?

问题描述

所以，我有一个对象，里面有很多不可腌制的东西(pygame 事件、orderedDicts、时钟等)，我需要将它保存到磁盘.

问题是，如果我可以让这个东西存储一个有进度的字符串(我只需要一个整数)，那么我可以将它传递给对象的 init，它会重建所有这些东西.不幸的是，我使用的框架 (Renpy) 会腌制对象并尝试加载它，尽管我可以将其保存为单个整数，但我无法更改.p>

所以，我要问的是，我怎样才能覆盖方法，以便当 pickle 尝试保存对象时，它只保存进度值，并且每当它尝试加载对象时，它都会从进度值?

我已经看到一些关于 __repr__ 方法的讨论，但我不确定在我的情况下如何使用它.

解决方案

你要找的钩子是 __reduce__.它应该返回一个 (callable, args) 元组；callable 和 args 将被序列化，并且在反序列化时，将通过 callable(*args) 重新创建对象.如果您的类的构造函数采用 int，您可以将 __reduce__ 实现为

类 ComplicatedThing:def __reduce__(self):返回 (ComplicatedThing, (self.progress_int,))

您可以在元组中添加一些可选的额外内容，当您的对象图具有循环依赖关系时最有用，但您在这里不需要它们.

So, I have an object that has quite a bit of non-pickleable things in it (pygame events, orderedDicts, clock, etc.) and I need to save it to disk.

Thing is, if I can just get this thing to store a string that has the progress (a single integer is all I need), then I can pass it to the object's init and it will rebuild all of those things. Unfortunately, a framework I am using (Renpy) will pickle the object and attempt to load it, despite the fact that I could save it as a single integer, and I can't change that.

So, what I'm asking is, how can I override methods so that whenever pickle tries to save the object, it saves only the progress value, and whenever it tries to load the object, it creates a new instance from the progress value?

I've seen a bit talking bout the __repr__ method, but I am unsure how I would use this in my situation.

解决方案

The hook you're looking for is __reduce__. It should return a (callable, args) tuple; the callable and args will be serialized, and on deserialization, the object will be recreated through callable(*args). If your class's constructor takes an int, you can implement __reduce__ as

class ComplicatedThing:
    def __reduce__(self):
        return (ComplicatedThing, (self.progress_int,))

There are a few optional extra things you can put into the tuple, mostly useful for when your object graph has cyclic dependencies, but you shouldn't need them here.