'''
Module to define the classes that support serialization for all JSON columns
A lot of persistable subclasses try to persist objects that cannot be natively serialized
in a database. This attempts to define a custom pattern to serialize them and
subsequently deserialize on load
'''
[docs]__author__ = 'Elisha Yadgaran'
import simplejson as json
import cloudpickle as pickle
import codecs
import sys
from decimal import Decimal
from datetime import datetime, timedelta
try: # Py2/3 compatibility
basestring
except NameError:
[docs]class JSONSerializer(json.JSONEncoder):
[docs] def default(self, obj):
if isinstance(obj, Decimal):
return float(obj)
if isinstance(obj, datetime):
return obj.__str__()
if isinstance(obj, timedelta):
return int(obj)
# Otherwise try defaults or fallback to pickle
try:
return super(JSONSerializer, self).default(obj)
except TypeError:
return 'pickle_serialized->' + codecs.encode(pickle.dumps(obj), "base64").decode()
[docs]def object_hook(data, ignore_dicts=False):
# if this is a string, check for pickled
if isinstance(data, basestring) and len(data) > 19:
if data[:19] == 'pickle_serialized->':
return pickle.loads(codecs.decode(data[19:].encode(), "base64"))
# if this is a list of values, return list of deserialized values
if isinstance(data, list):
return [object_hook(item, ignore_dicts=True) for item in data]
# if this is a dictionary, return dictionary of deserialized keys and values
# but only if we haven't already deserialized it
if isinstance(data, dict) and not ignore_dicts:
return {
object_hook(key, ignore_dicts=True): object_hook(value, ignore_dicts=True)
for key, value in data.items()
}
# if it's anything else, return it in its original form
return data
[docs]def custom_dumps(data):
# Unfortunately JSON doesnt support dict keys as ints so they will automatically
# get converted. Hopefully this wont be an issue in SimpleML, but be aware...
# Ignore NaN converts any non-native json types (NaN, Infinity, etc) to null. Native json library
# does not handle those and doesnt recognize them as unserializable (so overwriting default doesnt help)
return json.dumps(data, cls=JSONSerializer, ensure_ascii=False, ignore_nan=True)
[docs]def custom_loads(data):
# Need the extra nesting because json loads only passes nested dict objects to object_hook
# Python 2 strings have a decode method, python 3 doesn't
if sys.version_info[0] == 2:
return object_hook(json.loads(data.decode('utf-8'), object_hook=object_hook), ignore_dicts=True)
else:
return object_hook(json.loads(data, object_hook=object_hook), ignore_dicts=True)