sdjson

Custom JSON Encoder for Python utilising functools.singledispatch to support custom encoders for both Python's built-in classes and user-created classes, without as much legwork.

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Usage

Creating and registering a custom encoder is as easy as:

>>> import sdjson
>>>
>>> @sdjson.dump.register(MyClass)
>>> def encode_myclass(obj):
...     return dict(obj)
>>>

In this case, MyClass can be made JSON-serializable simply by calling dict() on it. If your class requires more complicated logic to make it JSON-serializable, do that here.

Then, to dump the object to a string:

>>> class_instance = MyClass()
>>> print(sdjson.dumps(class_instance))
'{"menu": ["egg and bacon", "egg sausage and bacon", "egg and spam", "egg bacon and spam"],
"today\'s special": "Lobster Thermidor au Crevette with a Mornay sauce served in a Provencale
manner with shallots and aubergines garnished with truffle pate, brandy and with a fried egg
on top and spam."}'
>>>

Or to dump to a file:

>>> with open("spam.json", "w") as fp:
...     sdjson.dumps(class_instance, fp)
...
>>>

sdjson also provides access to load, loads, JSONDecoder, JSONDecodeError, and JSONEncoder from the json module, allowing you to use sdjson as a drop-in replacement for json.

If you wish to dump an object without using the custom encoders, you can pass a different JSONEncoder subclass, or indeed JSONEncoder itself to get the stock functionality.

>>> sdjson.dumps(class_instance, cls=sdjson.JSONEncoder)
>>>

When you've finished, if you want to unregister the encoder you can call:

>>> sdjson.encoders.unregister(MyClass)
>>>

to remove the encoder for MyClass. If you want to replace the encoder with a different one it is not necessary to call this function: the @sdjson.encoders.register decorator will replace any existing decorator for the given class.

Note that this module cannot be used to create custom encoders for any object json already knows about; that is: dict, list, tuple, str, int, float, bool, and None.

TODO

1. Add support for custom decoders.