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copied!<p>You can't serialize arbitrary objects with <code>simplejson</code>. You need to pass a <code>default</code> and <code>object_hook</code> to <code>dump</code> and <code>load</code>. Here's an example:</p> <pre><code>class SerializerRegistry(object): def __init__(self): self._classes = {} def add(self, cls): self._classes[cls.__module__, cls.__name__] = cls return cls def object_hook(self, dct): module, cls_name = dct.pop('__type__', (None, None)) if cls_name is not None: return self._classes[module, cls_name].from_dict(dct) else: return dct def default(self, obj): dct = obj.to_dict() dct['__type__'] = [type(obj).__module__, type(obj).__name__] return dct registry = SerializerRegistry() @registry.add class A(object): def __init__(self, item1): self.item1 = item1 def __repr__(self): return str(self.__dict__) def to_dict(self): return dict(item1=self.item1) @classmethod def from_dict(cls, dct): return cls(**dct) s = json.dumps(A(1), default=registry.default) a = json.loads(s, object_hook=registry.object_hook) </code></pre> <p>This results in this:</p> <pre><code>>>> s '{"item1": 1, "__type__": ["__main__", "A"]}' >>> a {'item1': 1} </code></pre> <p>But what you really need is a function <code>default</code> that creates dictionary from the objects that you wish to serialize, and a function <code>object_hook</code> that returns an object (of the correct type) when it is given a dictionary if a dictionary isn't enough. The best approach is to have methods on the serializable classes that create a dict from the object and that construct it back, and also to have a mapping that recognizes to which class the dictionaries belong.</p> <p>You can also add an identifier to the classes to be used as an index for <code>_classes</code>. This way you wouldn't have issues if you have to move a class.</p>

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