/usr/lib/python2.7/dist-packages/jsonpickle/handlers.py is in python-jsonpickle 0.9.2-1.
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"""
Custom handlers may be created to handle other objects. Each custom handler
must derive from :class:`jsonpickle.handlers.BaseHandler` and
implement ``flatten`` and ``restore``.
A handler can be bound to other types by calling :func:`jsonpickle.handlers.register`.
:class:`jsonpickle.customhandlers.SimpleReduceHandler` is suitable for handling
objects that implement the reduce protocol::
from jsonpickle import handlers
class MyCustomObject(handlers.BaseHandler):
...
def __reduce__(self):
return MyCustomObject, self._get_args()
handlers.register(MyCustomObject, handlers.SimpleReduceHandler)
"""
import collections
import copy
import datetime
import decimal
import re
import sys
import time
from jsonpickle import util
from jsonpickle.compat import unicode
from jsonpickle.compat import queue
class Registry(object):
def __init__(self):
self._handlers = {}
self._base_handlers = {}
def get(self, cls_or_name, default=None):
"""
:param cls_or_name: the type or its fully qualified name
:param default: default value, if a matching handler is not found
Looks up a handler by type reference or its fully qualified name. If a direct match
is not found, the search is performed over all handlers registered with base=True.
"""
handler = self._handlers.get(cls_or_name)
if handler is None and util.is_type(cls_or_name): # attempt to find a base class
for cls, base_handler in self._base_handlers.items():
if issubclass(cls_or_name, cls):
return base_handler
return default if handler is None else handler
def register(self, cls, handler=None, base=False):
"""Register the a custom handler for a class
:param cls: The custom object class to handle
:param handler: The custom handler class (if None, a decorator wrapper is returned)
:param base: Indicates whether the handler should be registered for all subclasses
This function can be also used as a decorator by omitting the `handler` argument:
@jsonpickle.handlers.register(Foo, base=True)
class FooHandler(jsonpickle.handlers.BaseHandler):
pass
"""
if handler is None:
def _register(handler_cls):
self.register(cls, handler=handler_cls, base=base)
return handler_cls
return _register
if not util.is_type(cls):
raise TypeError('{0!r} is not a class/type'.format(cls))
# store both the name and the actual type for the ugly cases like
# _sre.SRE_Pattern that cannot be loaded back directly
self._handlers[util.importable_name(cls)] = self._handlers[cls] = handler
if base:
# only store the actual type for subclass checking
self._base_handlers[cls] = handler
def unregister(self, cls):
self._handlers.pop(cls, None)
self._handlers.pop(util.importable_name(cls), None)
self._base_handlers.pop(cls, None)
registry = Registry()
register = registry.register
unregister = registry.unregister
get = registry.get
class BaseHandler(object):
def __init__(self, context):
"""
Initialize a new handler to handle a registered type.
:Parameters:
- `context`: reference to pickler/unpickler
"""
self.context = context
def flatten(self, obj, data):
"""
Flatten `obj` into a json-friendly form and write result to `data`.
:param object obj: The object to be serialized.
:param dict data: A partially filled dictionary which will contain the
json-friendly representation of `obj` once this method has
finished.
"""
raise NotImplementedError('You must implement flatten() in %s' %
self.__class__)
def restore(self, obj):
"""
Restore an object of the registered type from the json-friendly
representation `obj` and return it.
"""
raise NotImplementedError('You must implement restore() in %s' %
self.__class__)
@classmethod
def handles(self, cls):
"""
Register this handler for the given class. Suitable as a decorator,
e.g.::
@SimpleReduceHandler.handles
class MyCustomClass:
def __reduce__(self):
...
"""
registry.register(cls, self)
return cls
class DatetimeHandler(BaseHandler):
"""Custom handler for datetime objects
Datetime objects use __reduce__, and they generate binary strings encoding
the payload. This handler encodes that payload to reconstruct the
object.
"""
def flatten(self, obj, data):
pickler = self.context
if not pickler.unpicklable:
return unicode(obj)
cls, args = obj.__reduce__()
flatten = pickler.flatten
payload = util.b64encode(args[0])
args = [payload] + [flatten(i, reset=False) for i in args[1:]]
data['__reduce__'] = (flatten(cls, reset=False), args)
return data
def restore(self, data):
cls, args = data['__reduce__']
unpickler = self.context
restore = unpickler.restore
cls = restore(cls, reset=False)
value = util.b64decode(args[0])
params = (value,) + tuple([restore(i, reset=False) for i in args[1:]])
return cls.__new__(cls, *params)
DatetimeHandler.handles(datetime.datetime)
DatetimeHandler.handles(datetime.date)
DatetimeHandler.handles(datetime.time)
class RegexHandler(BaseHandler):
"""Flatten _sre.SRE_Pattern (compiled regex) objects"""
def flatten(self, obj, data):
data['pattern'] = obj.pattern
return data
def restore(self, data):
return re.compile(data['pattern'])
RegexHandler.handles(type(re.compile('')))
class SimpleReduceHandler(BaseHandler):
"""Follow the __reduce__ protocol to pickle an object.
As long as the factory and its arguments are pickleable, this should
pickle any object that implements the reduce protocol.
"""
def flatten(self, obj, data):
flatten = self.context.flatten
data['__reduce__'] = [flatten(i, reset=False) for i in obj.__reduce__()]
return data
def restore(self, data):
restore = self.context.restore
factory, args = [restore(i, reset=False) for i in data['__reduce__']]
return factory(*args)
class OrderedDictReduceHandler(SimpleReduceHandler):
"""Serialize OrderedDict on Python 3.4+
Python 3.4+ returns multiple entries in an OrderedDict's
reduced form. Previous versions return a two-item tuple.
OrderedDictReduceHandler makes the formats compatible.
"""
def flatten(self, obj, data):
# __reduce__() on older pythons returned a list of
# [key, value] list pairs inside a tuple.
# Recreate that structure so that the file format
# is consistent between python versions.
flatten = self.context.flatten
reduced = obj.__reduce__()
factory = flatten(reduced[0], reset=False)
pairs = [list(x) for x in reduced[-1]]
args = flatten((pairs,), reset=False)
data['__reduce__'] = [factory, args]
return data
SimpleReduceHandler.handles(time.struct_time)
SimpleReduceHandler.handles(datetime.timedelta)
SimpleReduceHandler.handles(collections.deque)
if sys.version_info >= (2, 7):
SimpleReduceHandler.handles(collections.Counter)
if sys.version_info >= (3, 4):
OrderedDictReduceHandler.handles(collections.OrderedDict)
else:
SimpleReduceHandler.handles(collections.OrderedDict)
if sys.version_info >= (3, 0):
SimpleReduceHandler.handles(decimal.Decimal)
try:
import posix
SimpleReduceHandler.handles(posix.stat_result)
except ImportError:
pass
class QueueHandler(BaseHandler):
"""Opaquely serializes Queue objects
Queues contains mutex and condition variables which cannot be serialized.
Construct a new Queue instance when restoring.
"""
def flatten(self, obj, data):
return data
def restore(self, data):
return queue.Queue()
QueueHandler.handles(queue.Queue)
class CloneFactory(object):
"""Serialization proxy for collections.defaultdict's default_factory"""
def __init__(self, exemplar):
self.exemplar = exemplar
def __call__(self, clone=copy.copy):
"""Create new instances by making copies of the provided exemplar"""
return clone(self.exemplar)
def __repr__(self):
return ('<CloneFactory object at 0x%x (%s)>' % (id(self), self.exemplar))
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