How to make a class JSON serializable

json, python, serialization

Solution

Do you have an idea about the expected output? For example, will this do?

>>> f  = FileItem("/foo/bar")
>>> magic(f)
'{"fname": "/foo/bar"}'

In that case you can merely call `json.dumps(f.__dict__)`.

If you want more customized output then you will have to subclass `JSONEncoder` and implement your own custom serialization.

For a trivial example, see below.

>>> from json import JSONEncoder
>>> class MyEncoder(JSONEncoder):
        def default(self, o):
            return o.__dict__    

>>> MyEncoder().encode(f)
'{"fname": "/foo/bar"}'

Then you pass this class into the `json.dumps()` method as `cls` kwarg:

json.dumps(cls=MyEncoder)

If you also want to decode then you'll have to supply a custom `object_hook` to the `JSONDecoder` class. For example:

>>> def from_json(json_object):
        if 'fname' in json_object:
            return FileItem(json_object['fname'])
>>> f = JSONDecoder(object_hook = from_json).decode('{"fname": "/foo/bar"}')
>>> f
<__main__.FileItem object at 0x9337fac>
>>>

Problem

How to make a Python class serializable? ``` class FileItem: def __init__(self, fname): self.fname = fname ``` Attempt to serialize to JSON: ``` >>> import json >>> x = FileItem('/foo/bar') >>> json.dumps(x) TypeError: Object of type 'FileItem' is not JSON serializable ```

Original source

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