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# coding: utf-8
This modules implements custom types in SQLAlchemy.
from __future__ import absolute_import, print_function, unicode_literals
import json
import sqlalchemy.types as types
class StringyJSON(types.TypeDecorator):
Stores and retrieves JSON as TEXT for SQLite.
.. note :: The associated field is immutable. That is, changes to the data
(typically, changing the value of a dict field) will not trigger an update
on the SQL side upon ``commit`` as the reference to the object will not
have been updated. One should force the update by forcing an update of the
reference (by performing a ``copy`` operation on the dict for instance).
impl = types.TEXT
def process_bind_param(self, value, dialect):
Process the bound param, serialize the object to JSON before saving
into database.
if value is not None:
value = json.dumps(value)
return value
def process_result_value(self, value, dialect):
Process the value fetched from the database, deserialize the JSON
string before returning the object.
if value is not None:
value = json.loads(value)
return value
# TypeEngine.with_variant says "use StringyJSON instead when
# connecting to 'sqlite'"
# pylint: disable=locally-disabled,invalid-name
MagicJSON = types.JSON().with_variant(StringyJSON, 'sqlite')