Python JSON encoder to support datetime?

json.dumps(thing, default=str)

The docs suggest subclassing JSONEncoder and implementing your own default method. Seems like you're basically there, and it's not a "dirty hack".

The reason dates aren't handled by the default encoder is there is no standard representation of a date in JSON. Some people are using the format /Date(1198908717056)/, but I prefer ISO format personally.

import jsonimport datetimeclass DateTimeEncoder(json.JSONEncoder):    def default(self, obj):        if isinstance(obj, (datetime.datetime, datetime.date, datetime.time)):            return obj.isoformat()        elif isinstance(obj, datetime.timedelta):            return (datetime.datetime.min + obj).time().isoformat()        return super(DateTimeEncoder, self).default(obj)now = datetime.datetime.now()encoder = DateTimeEncoder()encoder.encode({"datetime": now, "date": now.date(), "time": now.time()})> {"datetime": "2019-07-02T16:17:09.990126", "date": "2019-07-02", "time": "16:17:09.990126"}

I made my own classes for my project:

import datetimeimport decimalimport jsonimport sysclass EnhancedJSONEncoder(json.JSONEncoder):    def default(self, obj):        if isinstance(obj, datetime.datetime):            ARGS = ('year', 'month', 'day', 'hour', 'minute',                     'second', 'microsecond')            return {'__type__': 'datetime.datetime',                    'args': [getattr(obj, a) for a in ARGS]}        elif isinstance(obj, datetime.date):            ARGS = ('year', 'month', 'day')            return {'__type__': 'datetime.date',                    'args': [getattr(obj, a) for a in ARGS]}        elif isinstance(obj, datetime.time):            ARGS = ('hour', 'minute', 'second', 'microsecond')            return {'__type__': 'datetime.time',                    'args': [getattr(obj, a) for a in ARGS]}        elif isinstance(obj, datetime.timedelta):            ARGS = ('days', 'seconds', 'microseconds')            return {'__type__': 'datetime.timedelta',                    'args': [getattr(obj, a) for a in ARGS]}        elif isinstance(obj, decimal.Decimal):            return {'__type__': 'decimal.Decimal',                    'args': [str(obj),]}        else:            return super().default(obj)class EnhancedJSONDecoder(json.JSONDecoder):    def __init__(self, *args, **kwargs):        super().__init__(*args, object_hook=self.object_hook,                         **kwargs)    def object_hook(self, d):         if '__type__' not in d:            return d        o = sys.modules[__name__]        for e in d['__type__'].split('.'):            o = getattr(o, e)        args, kwargs = d.get('args', ()), d.get('kwargs', {})        return o(*args, **kwargs)if __name__ == '__main__':    j1 = json.dumps({'now': datetime.datetime.now(),        'val': decimal.Decimal('9.3456789098765434987654567')},        cls=EnhancedJSONEncoder)    print(j1)    o1 = json.loads(j1, cls=EnhancedJSONDecoder)    print(o1)

Result:

{"val": {"args": ["9.3456789098765434987654567"], "__type__": "decimal.Decimal"}, "now": {"args": [2014, 4, 29, 11, 44, 57, 971600], "__type__": "datetime.datetime"}}{'val': Decimal('9.3456789098765434987654567'), 'now': datetime.datetime(2014, 4, 29, 11, 44, 57, 971600)}

References:

• json Documentation
• Mark Hildreth -- Subclassing JSONEncoder and JSONDecoder
• Cédric Krier -- trytond.protocols.jsonrpc source code

Note: It can be made more flexible by passing a custom dictionary with types as keys and args, kwargs as values to the encoder's __init__() and use that (or a default dictionary) in the default() method.