jsonlight 0.0.2.dev1

json with rudimentary type encoding/decoding for Python

Adds support for a couple of new Python magic methods to make Python object JSON encoding and decoding a bit easier.

Tutorial

Instead of:

from json import loads, dumps
from uuid import UUID, uuid4

obj = uuid4()
encoded = dumps(str(obj))
decoded = UUID(loads(encoded))

assert obj == decoded

You can do:

from jsonlight import loads, dumps
from uuid import UUID, uuid4

obj = uuid4()
encoded = dumps(obj)
decoded = loads(UUID, encoded)
assert obj == decoded

This is because jsonlight patches uuid.UUID class to add the following methods:

• __jsondump__: return a representation of self with JSON data types

• __jsonload__: instanciate an object based on the result from __jsondump__

You can see that the main difference with json.loads is that jsonlight.loads requires a type as first argument. This is because jsonlight.loads will first call json.loads to convert the string into a Python object with basic JSON tyes, and then pass that to the type’s __jsonload__ function.

Other types can’t be monkey patched, so you have to import them from jsonlight instead, which is the sad case of datetime:

from jsonlight import loads, dumps, datetime
obj = datetime.now()
assert obj == loads(datetime, dumps(obj))

You may also define __jsondump__ and __jsonload__ methods on your own classes, example:

from jsonlight import load

class YourClass:
    def __init__(self, uuid=None):
        self.uuid = uuid or uuid4()

    def __jsondump__(self):
        return dict(uuid=self.uuid)

    @classmethod
    def __jsonload__(cls, data):
        return cls(load(UUID, data['uuid'])

        # This also works, but would not illustrate how to support recursion
        # return cls(UUID(data['uuid']))

As you can see:

• you don’t have to worry about calling __jsondump__ on return values of your own __jsondump__ because jsonlight.dumps will do that recursively,

• you have full control on deserialization just like with __setstate__, but if you call jsonlight.load in there yourself then you don’t have to duplicate deserialization logic on nested objects,

Monkey-patches

Monkey-patched stdlib objects are:

• UUID

• Path

Feel free to add more.

Stdlib objects that couldn’t be monkey patched, and that you have to import from jsonlight instead are:

• datetime