Modular JSON Encoder. (With a register method for custom types)

mod-encoder.py

# Copyright (c) 2016 Muhammed Shamil K
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# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# The above copyright notice and this permission notice shall be included in
#  all copies or substantial portions of the Software.
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# THE SOFTWARE.

import json

"""\
This module contains a Modular JSON Encoder useful
for encoding custom Python objects and types. Simply
call it's `register_adapter` method and then give it as
the `cls` argment to `json.dump` or `json.dumps`. Like this:

    >>> from decimal import Decimal
    >>> ModularEncoder.register_adapter(Decimal, lambda dec: float(dec))
    >>> obj = {"something": Decimal(0.5746)}
    >>> json.dumps(obj, cls=ModularEncoder)


"""

class ModularEncoder(json.JSONEncoder):
    """\
    Custom JSON Encoder.

    Custom types can be added to the Encoder by calling
    the register_adapter method with the type of the
    object and a function to convert them to JSON serializable.

    Use it with JSON like this:

        >>> json.dumps(object ,cls=ModularEncoder)

    """
    defaults = {}

    @classmethod
    def register_adapter(self, type, func):
        """\
        Custom types can be added using this function.

        calling this method with a type/class and a function to decode
        it will make the Encoder call the function with the object
        that has the same type. The function should return a JSON serializable
        object.

        Eg:
            >>> from decimal import Decimal
            >>> ModularEncoder.register_adapter(Decimal, lambda dec: float(dec))

        """
        self.defaults[type] = func

    def default(self, o):
        func = self.defaults.get(type(o))
        if func:
            return func(o)
        return super().default(o)