Simple, datetime-aware JSON encoding/decoding in Python.

json_datetime.py

# Copyright (c) 2022, Jérémie Lumbroso <[email protected]>
#
# Simple datetime-aware JSON in Python
#
# Usage:
# - json_timestamp_loads just() like json.loads()
# - json_timestamp_dumps just() like json.dumps()


import datetime
import dateutil.parser
import json
import typing


KEYNAMES_WITH_TIMESTAMPS = [
    "date", "timestamp", "last_updated", "last_created", "last_edited",
]


class JSONDateTimeEncoder(json.JSONEncoder):
    """
    Subclass of `json.JSONEncoder` which is able to deserialize `datetime`
    and `date` objects.
    """

    # override the default method
    def default(self, obj: typing.Any) -> typing.Any:
        if isinstance(obj, (datetime.date, datetime.datetime)):
            return obj.isoformat()


def json_timestamp_decoder(obj: typing.Dict) -> typing.Dict:
    """
    Hook method that takes a dictionary and returns one in which qualifying
    have been parsed into `date` and `datetime` objects.
    """

    for key, value in obj.items():

        # check if key is susceptible to contain a date (a bit hackish!)
        if key not in KEYNAMES_WITH_TIMESTAMPS:
            continue

        # try to parse the datetime
        try:
            obj[key] = dateutil.parser.parse(value)
        except ValueError:
            pass

    return obj


def json_timestamp_loads(s, **kwargs):
    """
    Returns a Python object from `s` with `datetime` and `date` deserialization.
    """
    return json.loads(s, object_hook=json_timestamp_decoder, **kwargs)


def json_timestamp_dumps(obj, **kwargs):
    """
    Returns a JSON string representation of `obj` with `datetime` and
    `date` deserialization.
    """
    return json.dumps(
        obj,
        cls=JSONDateTimeEncoder,
        **kwargs,
    )