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� c �> � t | ||� � j |i |�� dS )ak Register a listener function for the given target.
The :func:`.listen` function is part of the primary interface for the
SQLAlchemy event system, documented at :ref:`event_toplevel`.
e.g.::
from sqlalchemy import event
from sqlalchemy.schema import UniqueConstraint
def unique_constraint_name(const, table):
const.name = "uq_%s_%s" % (
table.name,
list(const.columns)[0].name
)
event.listen(
UniqueConstraint,
"after_parent_attach",
unique_constraint_name)
A given function can also be invoked for only the first invocation
of the event using the ``once`` argument::
def on_config():
do_config()
event.listen(Mapper, "before_configure", on_config, once=True)
.. versionadded:: 0.9.4 Added ``once=True`` to :func:`.event.listen`
and :func:`.event.listens_for`.
.. warning:: The ``once`` argument does not imply automatic de-registration
of the listener function after it has been invoked a first time; a
listener entry will remain associated with the target object.
Associating an arbitrarily high number of listeners without explicitly
removing them will cause memory to grow unbounded even if ``once=True``
is specified.
.. note::
The :func:`.listen` function cannot be called at the same time
that the target event is being run. This has implications
for thread safety, and also means an event cannot be added
from inside the listener function for itself. The list of
events to be run are present inside of a mutable collection
that can't be changed during iteration.
Event registration and removal is not intended to be a "high
velocity" operation; it is a configurational operation. For
systems that need to quickly associate and deassociate with
events at high scale, use a mutable structure that is handled
from inside of a single listener.
.. versionchanged:: 1.0.0 - a ``collections.deque()`` object is now
used as the container for the list of events, which explicitly
disallows collection mutation while the collection is being
iterated.
.. seealso::
:func:`.listens_for`
:func:`.remove`
N)r �listen)r r r �args�kws r r r " s/ � �H .�J�v�z�2�&�&�-�t�:�r�:�:�:�:�:r c � � ���� ���� fd�}|S )a~ Decorate a function as a listener for the given target + identifier.
The :func:`.listens_for` decorator is part of the primary interface for the
SQLAlchemy event system, documented at :ref:`event_toplevel`.
e.g.::
from sqlalchemy import event
from sqlalchemy.schema import UniqueConstraint
@event.listens_for(UniqueConstraint, "after_parent_attach")
def unique_constraint_name(const, table):
const.name = "uq_%s_%s" % (
table.name,
list(const.columns)[0].name
)
A given function can also be invoked for only the first invocation
of the event using the ``once`` argument::
@event.listens_for(Mapper, "before_configure", once=True)
def on_config():
do_config()
.. versionadded:: 0.9.4 Added ``once=True`` to :func:`.event.listen`
and :func:`.event.listens_for`.
.. warning:: The ``once`` argument does not imply automatic de-registration
of the listener function after it has been invoked a first time; a
listener entry will remain associated with the target object.
Associating an arbitrarily high number of listeners without explicitly
removing them will cause memory to grow unbounded even if ``once=True``
is specified.
.. seealso::
:func:`.listen` - general description of event listening
c �, �� t ��| g��R i ��� | S )N)r )r r r r r s ����r �decoratez listens_for.<locals>.decorate� s* �� ��v�z�2�3��3�3�3��3�3�3�� r � )r r r r r s ```` r � listens_forr i s6 ����� �T� � � � � � � � �Or c �L � t | ||� � � � � dS )a Remove an event listener.
The arguments here should match exactly those which were sent to
:func:`.listen`; all the event registration which proceeded as a result
of this call will be reverted by calling :func:`.remove` with the same
arguments.
e.g.::
# if a function was registered like this...
@event.listens_for(SomeMappedClass, "before_insert", propagate=True)
def my_listener_function(*arg):
pass
# ... it's removed like this
event.remove(SomeMappedClass, "before_insert", my_listener_function)
Above, the listener function associated with ``SomeMappedClass`` was also
propagated to subclasses of ``SomeMappedClass``; the :func:`.remove`
function will revert all of these operations.
.. versionadded:: 0.9.0
.. note::
The :func:`.remove` function cannot be called at the same time
that the target event is being run. This has implications
for thread safety, and also means an event cannot be removed
from inside the listener function for itself. The list of
events to be run are present inside of a mutable collection
that can't be changed during iteration.
Event registration and removal is not intended to be a "high
velocity" operation; it is a configurational operation. For
systems that need to quickly associate and deassociate with
events at high scale, use a mutable structure that is handled
from inside of a single listener.
.. versionchanged:: 1.0.0 - a ``collections.deque()`` object is now
used as the container for the list of events, which explicitly
disallows collection mutation while the collection is being
iterated.
.. seealso::
:func:`.listen`
N)r �remove�r r r s r r" r" � s) � �b �v�z�2�&�&�-�-�/�/�/�/�/r c �H � t | ||� � � � � S )z`Return True if the given target/ident/fn is set up to listen.
.. versionadded:: 0.9.0
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