500 lines
16 KiB
Python
500 lines
16 KiB
Python
# orm/instrumentation.py
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# Copyright (C) 2005-2014 the SQLAlchemy authors and contributors <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""Defines SQLAlchemy's system of class instrumentation.
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This module is usually not directly visible to user applications, but
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defines a large part of the ORM's interactivity.
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instrumentation.py deals with registration of end-user classes
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for state tracking. It interacts closely with state.py
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and attributes.py which establish per-instance and per-class-attribute
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instrumentation, respectively.
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The class instrumentation system can be customized on a per-class
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or global basis using the :mod:`sqlalchemy.ext.instrumentation`
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module, which provides the means to build and specify
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alternate instrumentation forms.
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.. versionchanged: 0.8
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The instrumentation extension system was moved out of the
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ORM and into the external :mod:`sqlalchemy.ext.instrumentation`
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package. When that package is imported, it installs
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itself within sqlalchemy.orm so that its more comprehensive
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resolution mechanics take effect.
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"""
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from . import exc, collections, interfaces, state
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from .. import util
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from . import base
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class ClassManager(dict):
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"""tracks state information at the class level."""
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MANAGER_ATTR = base.DEFAULT_MANAGER_ATTR
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STATE_ATTR = base.DEFAULT_STATE_ATTR
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deferred_scalar_loader = None
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original_init = object.__init__
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factory = None
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def __init__(self, class_):
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self.class_ = class_
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self.info = {}
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self.new_init = None
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self.local_attrs = {}
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self.originals = {}
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self._bases = [mgr for mgr in [
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manager_of_class(base)
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for base in self.class_.__bases__
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if isinstance(base, type)
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] if mgr is not None]
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for base in self._bases:
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self.update(base)
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self.dispatch._events._new_classmanager_instance(class_, self)
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#events._InstanceEventsHold.populate(class_, self)
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for basecls in class_.__mro__:
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mgr = manager_of_class(basecls)
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if mgr is not None:
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self.dispatch._update(mgr.dispatch)
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self.manage()
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self._instrument_init()
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if '__del__' in class_.__dict__:
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util.warn("__del__() method on class %s will "
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"cause unreachable cycles and memory leaks, "
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"as SQLAlchemy instrumentation often creates "
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"reference cycles. Please remove this method." %
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class_)
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def __hash__(self):
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return id(self)
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def __eq__(self, other):
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return other is self
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@property
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def is_mapped(self):
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return 'mapper' in self.__dict__
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@util.memoized_property
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def mapper(self):
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# raises unless self.mapper has been assigned
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raise exc.UnmappedClassError(self.class_)
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def _all_sqla_attributes(self, exclude=None):
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"""return an iterator of all classbound attributes that are
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implement :class:`._InspectionAttr`.
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This includes :class:`.QueryableAttribute` as well as extension
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types such as :class:`.hybrid_property` and :class:`.AssociationProxy`.
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"""
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if exclude is None:
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exclude = set()
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for supercls in self.class_.__mro__:
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for key in set(supercls.__dict__).difference(exclude):
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exclude.add(key)
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val = supercls.__dict__[key]
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if isinstance(val, interfaces._InspectionAttr):
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yield key, val
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def _attr_has_impl(self, key):
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"""Return True if the given attribute is fully initialized.
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i.e. has an impl.
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"""
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return key in self and self[key].impl is not None
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def _subclass_manager(self, cls):
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"""Create a new ClassManager for a subclass of this ClassManager's
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class.
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This is called automatically when attributes are instrumented so that
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the attributes can be propagated to subclasses against their own
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class-local manager, without the need for mappers etc. to have already
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pre-configured managers for the full class hierarchy. Mappers
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can post-configure the auto-generated ClassManager when needed.
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"""
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manager = manager_of_class(cls)
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if manager is None:
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manager = _instrumentation_factory.create_manager_for_cls(cls)
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return manager
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def _instrument_init(self):
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# TODO: self.class_.__init__ is often the already-instrumented
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# __init__ from an instrumented superclass. We still need to make
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# our own wrapper, but it would
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# be nice to wrap the original __init__ and not our existing wrapper
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# of such, since this adds method overhead.
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self.original_init = self.class_.__init__
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self.new_init = _generate_init(self.class_, self)
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self.install_member('__init__', self.new_init)
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def _uninstrument_init(self):
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if self.new_init:
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self.uninstall_member('__init__')
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self.new_init = None
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@util.memoized_property
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def _state_constructor(self):
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self.dispatch.first_init(self, self.class_)
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return state.InstanceState
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def manage(self):
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"""Mark this instance as the manager for its class."""
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setattr(self.class_, self.MANAGER_ATTR, self)
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def dispose(self):
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"""Dissasociate this manager from its class."""
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delattr(self.class_, self.MANAGER_ATTR)
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@util.hybridmethod
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def manager_getter(self):
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return _default_manager_getter
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@util.hybridmethod
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def state_getter(self):
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"""Return a (instance) -> InstanceState callable.
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"state getter" callables should raise either KeyError or
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AttributeError if no InstanceState could be found for the
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instance.
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"""
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return _default_state_getter
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@util.hybridmethod
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def dict_getter(self):
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return _default_dict_getter
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def instrument_attribute(self, key, inst, propagated=False):
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if propagated:
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if key in self.local_attrs:
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return # don't override local attr with inherited attr
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else:
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self.local_attrs[key] = inst
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self.install_descriptor(key, inst)
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self[key] = inst
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for cls in self.class_.__subclasses__():
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manager = self._subclass_manager(cls)
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manager.instrument_attribute(key, inst, True)
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def subclass_managers(self, recursive):
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for cls in self.class_.__subclasses__():
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mgr = manager_of_class(cls)
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if mgr is not None and mgr is not self:
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yield mgr
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if recursive:
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for m in mgr.subclass_managers(True):
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yield m
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def post_configure_attribute(self, key):
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_instrumentation_factory.dispatch.\
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attribute_instrument(self.class_, key, self[key])
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def uninstrument_attribute(self, key, propagated=False):
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if key not in self:
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return
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if propagated:
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if key in self.local_attrs:
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return # don't get rid of local attr
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else:
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del self.local_attrs[key]
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self.uninstall_descriptor(key)
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del self[key]
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for cls in self.class_.__subclasses__():
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manager = manager_of_class(cls)
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if manager:
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manager.uninstrument_attribute(key, True)
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def unregister(self):
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"""remove all instrumentation established by this ClassManager."""
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self._uninstrument_init()
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self.mapper = self.dispatch = None
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self.info.clear()
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for key in list(self):
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if key in self.local_attrs:
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self.uninstrument_attribute(key)
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def install_descriptor(self, key, inst):
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if key in (self.STATE_ATTR, self.MANAGER_ATTR):
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raise KeyError("%r: requested attribute name conflicts with "
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"instrumentation attribute of the same name." %
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key)
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setattr(self.class_, key, inst)
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def uninstall_descriptor(self, key):
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delattr(self.class_, key)
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def install_member(self, key, implementation):
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if key in (self.STATE_ATTR, self.MANAGER_ATTR):
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raise KeyError("%r: requested attribute name conflicts with "
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"instrumentation attribute of the same name." %
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key)
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self.originals.setdefault(key, getattr(self.class_, key, None))
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setattr(self.class_, key, implementation)
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def uninstall_member(self, key):
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original = self.originals.pop(key, None)
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if original is not None:
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setattr(self.class_, key, original)
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def instrument_collection_class(self, key, collection_class):
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return collections.prepare_instrumentation(collection_class)
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def initialize_collection(self, key, state, factory):
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user_data = factory()
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adapter = collections.CollectionAdapter(
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self.get_impl(key), state, user_data)
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return adapter, user_data
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def is_instrumented(self, key, search=False):
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if search:
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return key in self
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else:
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return key in self.local_attrs
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def get_impl(self, key):
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return self[key].impl
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@property
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def attributes(self):
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return iter(self.values())
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## InstanceState management
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def new_instance(self, state=None):
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instance = self.class_.__new__(self.class_)
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setattr(instance, self.STATE_ATTR,
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state or self._state_constructor(instance, self))
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return instance
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def setup_instance(self, instance, state=None):
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setattr(instance, self.STATE_ATTR,
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state or self._state_constructor(instance, self))
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def teardown_instance(self, instance):
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delattr(instance, self.STATE_ATTR)
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def _serialize(self, state, state_dict):
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return _SerializeManager(state, state_dict)
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def _new_state_if_none(self, instance):
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"""Install a default InstanceState if none is present.
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A private convenience method used by the __init__ decorator.
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"""
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if hasattr(instance, self.STATE_ATTR):
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return False
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elif self.class_ is not instance.__class__ and \
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self.is_mapped:
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# this will create a new ClassManager for the
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# subclass, without a mapper. This is likely a
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# user error situation but allow the object
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# to be constructed, so that it is usable
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# in a non-ORM context at least.
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return self._subclass_manager(instance.__class__).\
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_new_state_if_none(instance)
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else:
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state = self._state_constructor(instance, self)
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setattr(instance, self.STATE_ATTR, state)
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return state
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def has_state(self, instance):
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return hasattr(instance, self.STATE_ATTR)
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def has_parent(self, state, key, optimistic=False):
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"""TODO"""
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return self.get_impl(key).hasparent(state, optimistic=optimistic)
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def __bool__(self):
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"""All ClassManagers are non-zero regardless of attribute state."""
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return True
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__nonzero__ = __bool__
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def __repr__(self):
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return '<%s of %r at %x>' % (
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self.__class__.__name__, self.class_, id(self))
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class _SerializeManager(object):
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"""Provide serialization of a :class:`.ClassManager`.
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The :class:`.InstanceState` uses ``__init__()`` on serialize
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and ``__call__()`` on deserialize.
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"""
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def __init__(self, state, d):
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self.class_ = state.class_
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manager = state.manager
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manager.dispatch.pickle(state, d)
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def __call__(self, state, inst, state_dict):
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state.manager = manager = manager_of_class(self.class_)
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if manager is None:
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raise exc.UnmappedInstanceError(
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inst,
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"Cannot deserialize object of type %r - "
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"no mapper() has "
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"been configured for this class within the current "
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"Python process!" %
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self.class_)
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elif manager.is_mapped and not manager.mapper.configured:
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manager.mapper._configure_all()
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# setup _sa_instance_state ahead of time so that
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# unpickle events can access the object normally.
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# see [ticket:2362]
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if inst is not None:
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manager.setup_instance(inst, state)
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manager.dispatch.unpickle(state, state_dict)
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class InstrumentationFactory(object):
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"""Factory for new ClassManager instances."""
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def create_manager_for_cls(self, class_):
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assert class_ is not None
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assert manager_of_class(class_) is None
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# give a more complicated subclass
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# a chance to do what it wants here
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manager, factory = self._locate_extended_factory(class_)
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if factory is None:
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factory = ClassManager
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manager = factory(class_)
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self._check_conflicts(class_, factory)
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manager.factory = factory
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self.dispatch.class_instrument(class_)
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return manager
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def _locate_extended_factory(self, class_):
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"""Overridden by a subclass to do an extended lookup."""
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return None, None
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def _check_conflicts(self, class_, factory):
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"""Overridden by a subclass to test for conflicting factories."""
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return
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def unregister(self, class_):
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manager = manager_of_class(class_)
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manager.unregister()
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manager.dispose()
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self.dispatch.class_uninstrument(class_)
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if ClassManager.MANAGER_ATTR in class_.__dict__:
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delattr(class_, ClassManager.MANAGER_ATTR)
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# this attribute is replaced by sqlalchemy.ext.instrumentation
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# when importred.
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_instrumentation_factory = InstrumentationFactory()
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# these attributes are replaced by sqlalchemy.ext.instrumentation
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# when a non-standard InstrumentationManager class is first
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# used to instrument a class.
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instance_state = _default_state_getter = base.instance_state
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instance_dict = _default_dict_getter = base.instance_dict
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manager_of_class = _default_manager_getter = base.manager_of_class
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def register_class(class_):
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"""Register class instrumentation.
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Returns the existing or newly created class manager.
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"""
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manager = manager_of_class(class_)
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if manager is None:
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manager = _instrumentation_factory.create_manager_for_cls(class_)
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return manager
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def unregister_class(class_):
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"""Unregister class instrumentation."""
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_instrumentation_factory.unregister(class_)
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def is_instrumented(instance, key):
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"""Return True if the given attribute on the given instance is
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instrumented by the attributes package.
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This function may be used regardless of instrumentation
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applied directly to the class, i.e. no descriptors are required.
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"""
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return manager_of_class(instance.__class__).\
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is_instrumented(key, search=True)
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def _generate_init(class_, class_manager):
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"""Build an __init__ decorator that triggers ClassManager events."""
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# TODO: we should use the ClassManager's notion of the
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# original '__init__' method, once ClassManager is fixed
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# to always reference that.
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original__init__ = class_.__init__
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assert original__init__
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# Go through some effort here and don't change the user's __init__
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# calling signature, including the unlikely case that it has
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# a return value.
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# FIXME: need to juggle local names to avoid constructor argument
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# clashes.
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func_body = """\
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def __init__(%(apply_pos)s):
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new_state = class_manager._new_state_if_none(%(self_arg)s)
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if new_state:
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return new_state._initialize_instance(%(apply_kw)s)
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else:
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return original__init__(%(apply_kw)s)
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"""
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func_vars = util.format_argspec_init(original__init__, grouped=False)
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func_text = func_body % func_vars
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if util.py2k:
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func = getattr(original__init__, 'im_func', original__init__)
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func_defaults = getattr(func, 'func_defaults', None)
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else:
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func_defaults = getattr(original__init__, '__defaults__', None)
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func_kw_defaults = getattr(original__init__, '__kwdefaults__', None)
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env = locals().copy()
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exec(func_text, env)
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__init__ = env['__init__']
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__init__.__doc__ = original__init__.__doc__
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if func_defaults:
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__init__.__defaults__ = func_defaults
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if not util.py2k and func_kw_defaults:
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__init__.__kwdefaults__ = func_kw_defaults
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return __init__
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