Update 2025-04-24_11:44:19
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oib
472
venv/lib/python3.11/site-packages/sqlalchemy/event/base.py
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472
venv/lib/python3.11/site-packages/sqlalchemy/event/base.py
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# event/base.py
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# Copyright (C) 2005-2025 the SQLAlchemy authors and contributors
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# <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: https://www.opensource.org/licenses/mit-license.php
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"""Base implementation classes.
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The public-facing ``Events`` serves as the base class for an event interface;
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its public attributes represent different kinds of events. These attributes
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are mirrored onto a ``_Dispatch`` class, which serves as a container for
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collections of listener functions. These collections are represented both
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at the class level of a particular ``_Dispatch`` class as well as within
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instances of ``_Dispatch``.
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"""
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from __future__ import annotations
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import typing
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from typing import Any
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from typing import cast
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from typing import Dict
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from typing import Generic
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from typing import Iterator
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from typing import List
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from typing import Mapping
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from typing import MutableMapping
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from typing import Optional
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from typing import overload
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from typing import Tuple
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from typing import Type
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from typing import Union
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import weakref
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from .attr import _ClsLevelDispatch
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from .attr import _EmptyListener
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from .attr import _InstanceLevelDispatch
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from .attr import _JoinedListener
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from .registry import _ET
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from .registry import _EventKey
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from .. import util
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from ..util.typing import Literal
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_registrars: MutableMapping[str, List[Type[_HasEventsDispatch[Any]]]] = (
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util.defaultdict(list)
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)
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def _is_event_name(name: str) -> bool:
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# _sa_event prefix is special to support internal-only event names.
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# most event names are just plain method names that aren't
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# underscored.
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return (
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not name.startswith("_") and name != "dispatch"
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) or name.startswith("_sa_event")
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class _UnpickleDispatch:
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"""Serializable callable that re-generates an instance of
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:class:`_Dispatch` given a particular :class:`.Events` subclass.
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"""
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def __call__(self, _instance_cls: Type[_ET]) -> _Dispatch[_ET]:
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for cls in _instance_cls.__mro__:
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if "dispatch" in cls.__dict__:
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return cast(
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"_Dispatch[_ET]", cls.__dict__["dispatch"].dispatch
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)._for_class(_instance_cls)
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else:
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raise AttributeError("No class with a 'dispatch' member present.")
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class _DispatchCommon(Generic[_ET]):
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__slots__ = ()
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_instance_cls: Optional[Type[_ET]]
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def _join(self, other: _DispatchCommon[_ET]) -> _JoinedDispatcher[_ET]:
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raise NotImplementedError()
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def __getattr__(self, name: str) -> _InstanceLevelDispatch[_ET]:
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raise NotImplementedError()
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@property
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def _events(self) -> Type[_HasEventsDispatch[_ET]]:
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raise NotImplementedError()
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class _Dispatch(_DispatchCommon[_ET]):
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"""Mirror the event listening definitions of an Events class with
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listener collections.
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Classes which define a "dispatch" member will return a
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non-instantiated :class:`._Dispatch` subclass when the member
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is accessed at the class level. When the "dispatch" member is
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accessed at the instance level of its owner, an instance
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of the :class:`._Dispatch` class is returned.
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A :class:`._Dispatch` class is generated for each :class:`.Events`
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class defined, by the :meth:`._HasEventsDispatch._create_dispatcher_class`
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method. The original :class:`.Events` classes remain untouched.
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This decouples the construction of :class:`.Events` subclasses from
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the implementation used by the event internals, and allows
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inspecting tools like Sphinx to work in an unsurprising
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way against the public API.
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"""
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# "active_history" is an ORM case we add here. ideally a better
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# system would be in place for ad-hoc attributes.
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__slots__ = "_parent", "_instance_cls", "__dict__", "_empty_listeners"
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_active_history: bool
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_empty_listener_reg: MutableMapping[
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Type[_ET], Dict[str, _EmptyListener[_ET]]
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] = weakref.WeakKeyDictionary()
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_empty_listeners: Dict[str, _EmptyListener[_ET]]
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_event_names: List[str]
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_instance_cls: Optional[Type[_ET]]
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_joined_dispatch_cls: Type[_JoinedDispatcher[_ET]]
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_events: Type[_HasEventsDispatch[_ET]]
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"""reference back to the Events class.
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Bidirectional against _HasEventsDispatch.dispatch
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"""
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def __init__(
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self,
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parent: Optional[_Dispatch[_ET]],
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instance_cls: Optional[Type[_ET]] = None,
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):
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self._parent = parent
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self._instance_cls = instance_cls
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if instance_cls:
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assert parent is not None
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try:
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self._empty_listeners = self._empty_listener_reg[instance_cls]
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except KeyError:
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self._empty_listeners = self._empty_listener_reg[
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instance_cls
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] = {
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ls.name: _EmptyListener(ls, instance_cls)
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for ls in parent._event_descriptors
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}
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else:
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self._empty_listeners = {}
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def __getattr__(self, name: str) -> _InstanceLevelDispatch[_ET]:
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# Assign EmptyListeners as attributes on demand
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# to reduce startup time for new dispatch objects.
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try:
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ls = self._empty_listeners[name]
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except KeyError:
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raise AttributeError(name)
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else:
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setattr(self, ls.name, ls)
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return ls
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@property
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def _event_descriptors(self) -> Iterator[_ClsLevelDispatch[_ET]]:
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for k in self._event_names:
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# Yield _ClsLevelDispatch related
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# to relevant event name.
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yield getattr(self, k)
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def _listen(self, event_key: _EventKey[_ET], **kw: Any) -> None:
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return self._events._listen(event_key, **kw)
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def _for_class(self, instance_cls: Type[_ET]) -> _Dispatch[_ET]:
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return self.__class__(self, instance_cls)
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def _for_instance(self, instance: _ET) -> _Dispatch[_ET]:
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instance_cls = instance.__class__
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return self._for_class(instance_cls)
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def _join(self, other: _DispatchCommon[_ET]) -> _JoinedDispatcher[_ET]:
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"""Create a 'join' of this :class:`._Dispatch` and another.
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This new dispatcher will dispatch events to both
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:class:`._Dispatch` objects.
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"""
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assert "_joined_dispatch_cls" in self.__class__.__dict__
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return self._joined_dispatch_cls(self, other)
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def __reduce__(self) -> Union[str, Tuple[Any, ...]]:
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return _UnpickleDispatch(), (self._instance_cls,)
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def _update(
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self, other: _Dispatch[_ET], only_propagate: bool = True
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) -> None:
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"""Populate from the listeners in another :class:`_Dispatch`
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object."""
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for ls in other._event_descriptors:
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if isinstance(ls, _EmptyListener):
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continue
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getattr(self, ls.name).for_modify(self)._update(
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ls, only_propagate=only_propagate
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)
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def _clear(self) -> None:
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for ls in self._event_descriptors:
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ls.for_modify(self).clear()
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def _remove_dispatcher(cls: Type[_HasEventsDispatch[_ET]]) -> None:
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for k in cls.dispatch._event_names:
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_registrars[k].remove(cls)
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if not _registrars[k]:
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del _registrars[k]
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class _HasEventsDispatch(Generic[_ET]):
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_dispatch_target: Optional[Type[_ET]]
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"""class which will receive the .dispatch collection"""
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dispatch: _Dispatch[_ET]
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"""reference back to the _Dispatch class.
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Bidirectional against _Dispatch._events
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"""
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if typing.TYPE_CHECKING:
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def __getattr__(self, name: str) -> _InstanceLevelDispatch[_ET]: ...
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def __init_subclass__(cls) -> None:
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"""Intercept new Event subclasses and create associated _Dispatch
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classes."""
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cls._create_dispatcher_class(cls.__name__, cls.__bases__, cls.__dict__)
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@classmethod
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def _accept_with(
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cls, target: Union[_ET, Type[_ET]], identifier: str
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) -> Optional[Union[_ET, Type[_ET]]]:
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raise NotImplementedError()
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@classmethod
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def _listen(
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cls,
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event_key: _EventKey[_ET],
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*,
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propagate: bool = False,
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insert: bool = False,
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named: bool = False,
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asyncio: bool = False,
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) -> None:
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raise NotImplementedError()
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@staticmethod
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def _set_dispatch(
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klass: Type[_HasEventsDispatch[_ET]],
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dispatch_cls: Type[_Dispatch[_ET]],
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) -> _Dispatch[_ET]:
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# This allows an Events subclass to define additional utility
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# methods made available to the target via
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# "self.dispatch._events.<utilitymethod>"
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# @staticmethod to allow easy "super" calls while in a metaclass
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# constructor.
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klass.dispatch = dispatch_cls(None)
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dispatch_cls._events = klass
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return klass.dispatch
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@classmethod
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def _create_dispatcher_class(
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cls, classname: str, bases: Tuple[type, ...], dict_: Mapping[str, Any]
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) -> None:
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"""Create a :class:`._Dispatch` class corresponding to an
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:class:`.Events` class."""
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# there's all kinds of ways to do this,
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# i.e. make a Dispatch class that shares the '_listen' method
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# of the Event class, this is the straight monkeypatch.
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if hasattr(cls, "dispatch"):
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dispatch_base = cls.dispatch.__class__
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else:
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dispatch_base = _Dispatch
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event_names = [k for k in dict_ if _is_event_name(k)]
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dispatch_cls = cast(
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"Type[_Dispatch[_ET]]",
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type(
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"%sDispatch" % classname,
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(dispatch_base,),
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{"__slots__": event_names},
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),
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)
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dispatch_cls._event_names = event_names
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dispatch_inst = cls._set_dispatch(cls, dispatch_cls)
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for k in dispatch_cls._event_names:
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setattr(dispatch_inst, k, _ClsLevelDispatch(cls, dict_[k]))
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_registrars[k].append(cls)
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for super_ in dispatch_cls.__bases__:
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if issubclass(super_, _Dispatch) and super_ is not _Dispatch:
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for ls in super_._events.dispatch._event_descriptors:
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setattr(dispatch_inst, ls.name, ls)
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dispatch_cls._event_names.append(ls.name)
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if getattr(cls, "_dispatch_target", None):
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dispatch_target_cls = cls._dispatch_target
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assert dispatch_target_cls is not None
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if (
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hasattr(dispatch_target_cls, "__slots__")
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and "_slots_dispatch" in dispatch_target_cls.__slots__
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):
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dispatch_target_cls.dispatch = slots_dispatcher(cls)
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else:
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dispatch_target_cls.dispatch = dispatcher(cls)
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klass = type(
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"Joined%s" % dispatch_cls.__name__,
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(_JoinedDispatcher,),
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{"__slots__": event_names},
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)
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dispatch_cls._joined_dispatch_cls = klass
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# establish pickle capability by adding it to this module
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globals()[klass.__name__] = klass
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class _JoinedDispatcher(_DispatchCommon[_ET]):
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"""Represent a connection between two _Dispatch objects."""
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__slots__ = "local", "parent", "_instance_cls"
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local: _DispatchCommon[_ET]
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parent: _DispatchCommon[_ET]
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_instance_cls: Optional[Type[_ET]]
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def __init__(
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self, local: _DispatchCommon[_ET], parent: _DispatchCommon[_ET]
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):
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self.local = local
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self.parent = parent
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self._instance_cls = self.local._instance_cls
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def __reduce__(self) -> Any:
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return (self.__class__, (self.local, self.parent))
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def __getattr__(self, name: str) -> _JoinedListener[_ET]:
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# Assign _JoinedListeners as attributes on demand
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# to reduce startup time for new dispatch objects.
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ls = getattr(self.local, name)
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jl = _JoinedListener(self.parent, ls.name, ls)
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setattr(self, ls.name, jl)
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return jl
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def _listen(self, event_key: _EventKey[_ET], **kw: Any) -> None:
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return self.parent._listen(event_key, **kw)
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@property
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def _events(self) -> Type[_HasEventsDispatch[_ET]]:
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return self.parent._events
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class Events(_HasEventsDispatch[_ET]):
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"""Define event listening functions for a particular target type."""
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@classmethod
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def _accept_with(
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cls, target: Union[_ET, Type[_ET]], identifier: str
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) -> Optional[Union[_ET, Type[_ET]]]:
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def dispatch_is(*types: Type[Any]) -> bool:
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return all(isinstance(target.dispatch, t) for t in types)
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def dispatch_parent_is(t: Type[Any]) -> bool:
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parent = cast("_JoinedDispatcher[_ET]", target.dispatch).parent
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while isinstance(parent, _JoinedDispatcher):
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parent = cast("_JoinedDispatcher[_ET]", parent).parent
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return isinstance(parent, t)
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# Mapper, ClassManager, Session override this to
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# also accept classes, scoped_sessions, sessionmakers, etc.
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if hasattr(target, "dispatch"):
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if (
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dispatch_is(cls.dispatch.__class__)
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or dispatch_is(type, cls.dispatch.__class__)
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or (
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dispatch_is(_JoinedDispatcher)
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and dispatch_parent_is(cls.dispatch.__class__)
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)
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):
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return target
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return None
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@classmethod
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def _listen(
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cls,
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event_key: _EventKey[_ET],
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*,
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propagate: bool = False,
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insert: bool = False,
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named: bool = False,
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asyncio: bool = False,
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) -> None:
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event_key.base_listen(
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propagate=propagate, insert=insert, named=named, asyncio=asyncio
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)
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@classmethod
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def _remove(cls, event_key: _EventKey[_ET]) -> None:
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event_key.remove()
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@classmethod
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def _clear(cls) -> None:
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cls.dispatch._clear()
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class dispatcher(Generic[_ET]):
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"""Descriptor used by target classes to
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deliver the _Dispatch class at the class level
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and produce new _Dispatch instances for target
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instances.
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"""
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def __init__(self, events: Type[_HasEventsDispatch[_ET]]):
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self.dispatch = events.dispatch
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self.events = events
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@overload
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def __get__(
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self, obj: Literal[None], cls: Type[Any]
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) -> Type[_Dispatch[_ET]]: ...
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@overload
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def __get__(self, obj: Any, cls: Type[Any]) -> _DispatchCommon[_ET]: ...
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def __get__(self, obj: Any, cls: Type[Any]) -> Any:
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if obj is None:
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return self.dispatch
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disp = self.dispatch._for_instance(obj)
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try:
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obj.__dict__["dispatch"] = disp
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except AttributeError as ae:
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raise TypeError(
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"target %r doesn't have __dict__, should it be "
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"defining _slots_dispatch?" % (obj,)
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) from ae
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return disp
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class slots_dispatcher(dispatcher[_ET]):
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def __get__(self, obj: Any, cls: Type[Any]) -> Any:
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if obj is None:
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return self.dispatch
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if hasattr(obj, "_slots_dispatch"):
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return obj._slots_dispatch
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disp = self.dispatch._for_instance(obj)
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obj._slots_dispatch = disp
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return disp
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