Created
February 2, 2011 23:53
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JSON serializer that can proxy non-standard Python types
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import json | |
import datetime | |
try: | |
import iso8601 | |
except ImportError: | |
iso8601 = None | |
class FancyJSONEncoder(json.JSONEncoder): | |
_registry = {} | |
def __call__(self, obj, **kwargs): | |
''' | |
Pass object trough all encoders. | |
''' | |
for cls in self._registry: | |
checker, encoder = self._registry[cls] | |
if checker(obj): | |
return {'__proxy__': cls, 'value': encoder(obj)} | |
return obj | |
def register(self, cls, checker, encoder): | |
self._registry[cls] = (checker, encoder) | |
class FancyJSONDecoder(object): | |
_registry = {} | |
def __call__(self, obj, **kwargs): | |
''' | |
Pass object trough all decoders. | |
''' | |
try: | |
cls = obj['__proxy__'] | |
except: | |
return obj | |
else: | |
try: | |
decoder = self._registry[cls] | |
except KeyError: | |
raise ValueError("JSON decoder for %r not registered." % (cls,)) | |
else: | |
return decoder(obj['value']) | |
def register(self, cls, decoder): | |
self._registry[cls] = decoder | |
def unregister(self, cls): | |
try: | |
del self._registry[cls] | |
except: | |
pass | |
ENCODER = FancyJSONEncoder() | |
DECODER = FancyJSONDecoder() | |
# complex encoder | |
ENCODER.register('complex', | |
lambda obj: isinstance(obj, complex), | |
lambda obj: [obj.real, obj.imag]) | |
DECODER.register('complex', | |
lambda obj: complex(*obj)) | |
# Ellipsis encoded | |
ENCODER.register('ellipsis', | |
lambda obj: obj == Ellipsis, | |
lambda obj: None) | |
DECODER.register('ellipsis', | |
lambda obj: Ellipsis) | |
# set encoder | |
ENCODER.register('set', | |
lambda obj: isinstance(obj, set), | |
lambda obj: list(obj)) | |
DECODER.register('set', | |
lambda obj: set(obj)) | |
if iso8601: | |
# datetime.date encoder | |
ENCODER.register('date', | |
lambda obj: isinstance(obj, datetime.date), | |
lambda obj: obj.isoformat()) | |
DECODER.register('date', | |
lambda obj: iso8601.parse_date(obj)) | |
# datetime.datetime encoder | |
ENCODER.register('datetime', | |
lambda obj: isinstance(obj, datetime.datetime), | |
lambda obj: obj.isoformat()) | |
DECODER.register('datetime', | |
lambda obj: iso8601.parse_date(obj)) | |
def json_dump(obj): | |
return json.dumps(obj, default=ENCODER) | |
def json_load(obj, *args, **kwargs): | |
return json.loads(obj, object_hook=DECODER) | |
if __name__ == '__main__': | |
import pprint | |
ppr = pprint.PrettyPrinter() | |
now = datetime.datetime.now() | |
test1 = json_dump({ | |
'now': now, | |
'set': set((1,2,3,4,42,42,23,23)), | |
'ell': Ellipsis, | |
'complex': 23+42j, | |
}) | |
ppr.pprint(test1) | |
test2 = json_load(test1) | |
ppr.pprint(test2) | |
ppr.pprint(test1 == test2) | |
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