def instrument_class(self, mapper, class_):
r"""Receive a class when the mapper is first constructed,
before instrumentation is applied to the mapped class.
This event is the earliest phase of mapper construction.
Most attributes of the mapper are not yet initialized.
This listener can either be applied to the :class:`.Mapper`
class overall, or to any un-mapped class which serves as a base
for classes that will be mapped (using the ``propagate=True`` flag)::
Base = declarative_base()
@event.listens_for(Base, "instrument_class", propagate=True)
def on_new_class(mapper, cls_):
" ... "
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param class\_: the mapped class.
"""
python类listens_for()的实例源码
def before_compile(self, query):
"""Receive the :class:`.Query` object before it is composed into a
core :class:`.Select` object.
This event is intended to allow changes to the query given::
@event.listens_for(Query, "before_compile", retval=True)
def no_deleted(query):
for desc in query.column_descriptions:
if desc['type'] is User:
entity = desc['entity']
query = query.filter(entity.deleted == False)
return query
The event should normally be listened with the ``retval=True``
parameter set, so that the modified query may be returned.
"""
def instrument_class(self, mapper, class_):
r"""Receive a class when the mapper is first constructed,
before instrumentation is applied to the mapped class.
This event is the earliest phase of mapper construction.
Most attributes of the mapper are not yet initialized.
This listener can either be applied to the :class:`.Mapper`
class overall, or to any un-mapped class which serves as a base
for classes that will be mapped (using the ``propagate=True`` flag)::
Base = declarative_base()
@event.listens_for(Base, "instrument_class", propagate=True)
def on_new_class(mapper, cls_):
" ... "
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param class\_: the mapped class.
"""
def before_compile(self, query):
"""Receive the :class:`.Query` object before it is composed into a
core :class:`.Select` object.
This event is intended to allow changes to the query given::
@event.listens_for(Query, "before_compile", retval=True)
def no_deleted(query):
for desc in query.column_descriptions:
if desc['type'] is User:
entity = desc['entity']
query = query.filter(entity.deleted == False)
return query
The event should normally be listened with the ``retval=True``
parameter set, so that the modified query may be returned.
"""
def instrument_class(self, mapper, class_):
r"""Receive a class when the mapper is first constructed,
before instrumentation is applied to the mapped class.
This event is the earliest phase of mapper construction.
Most attributes of the mapper are not yet initialized.
This listener can either be applied to the :class:`.Mapper`
class overall, or to any un-mapped class which serves as a base
for classes that will be mapped (using the ``propagate=True`` flag)::
Base = declarative_base()
@event.listens_for(Base, "instrument_class", propagate=True)
def on_new_class(mapper, cls_):
" ... "
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param class\_: the mapped class.
"""
def before_compile(self, query):
"""Receive the :class:`.Query` object before it is composed into a
core :class:`.Select` object.
This event is intended to allow changes to the query given::
@event.listens_for(Query, "before_compile", retval=True)
def no_deleted(query):
for desc in query.column_descriptions:
if desc['type'] is User:
entity = desc['entity']
query = query.filter(entity.deleted == False)
return query
The event should normally be listened with the ``retval=True``
parameter set, so that the modified query may be returned.
"""
def instrument_class(self, mapper, class_):
"""Receive a class when the mapper is first constructed,
before instrumentation is applied to the mapped class.
This event is the earliest phase of mapper construction.
Most attributes of the mapper are not yet initialized.
This listener can either be applied to the :class:`.Mapper`
class overall, or to any un-mapped class which serves as a base
for classes that will be mapped (using the ``propagate=True`` flag)::
Base = declarative_base()
@event.listens_for(Base, "instrument_class", propagate=True)
def on_new_class(mapper, cls_):
" ... "
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param class\_: the mapped class.
"""
def before_compile(self, query):
"""Receive the :class:`.Query` object before it is composed into a
core :class:`.Select` object.
This event is intended to allow changes to the query given::
@event.listens_for(Query, "before_compile", retval=True)
def no_deleted(query):
for desc in query.column_descriptions:
if desc['type'] is User:
entity = desc['entity']
query = query.filter(entity.deleted == False)
return query
The event should normally be listened with the ``retval=True``
parameter set, so that the modified query may be returned.
"""
def instrument_class(self, mapper, class_):
"""Receive a class when the mapper is first constructed,
before instrumentation is applied to the mapped class.
This event is the earliest phase of mapper construction.
Most attributes of the mapper are not yet initialized.
This listener can either be applied to the :class:`.Mapper`
class overall, or to any un-mapped class which serves as a base
for classes that will be mapped (using the ``propagate=True`` flag)::
Base = declarative_base()
@event.listens_for(Base, "instrument_class", propagate=True)
def on_new_class(mapper, cls_):
" ... "
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param class\_: the mapped class.
"""
def before_compile(self, query):
"""Receive the :class:`.Query` object before it is composed into a
core :class:`.Select` object.
This event is intended to allow changes to the query given::
@event.listens_for(Query, "before_compile", retval=True)
def no_deleted(query):
for desc in query.column_descriptions:
if desc['type'] is User:
entity = desc['entity']
query = query.filter(entity.deleted == False)
return query
The event should normally be listened with the ``retval=True``
parameter set, so that the modified query may be returned.
"""
def after_soft_rollback(self, session, previous_transaction):
"""Execute after any rollback has occurred, including "soft"
rollbacks that don't actually emit at the DBAPI level.
This corresponds to both nested and outer rollbacks, i.e.
the innermost rollback that calls the DBAPI's
rollback() method, as well as the enclosing rollback
calls that only pop themselves from the transaction stack.
The given :class:`.Session` can be used to invoke SQL and
:meth:`.Session.query` operations after an outermost rollback
by first checking the :attr:`.Session.is_active` flag::
@event.listens_for(Session, "after_soft_rollback")
def do_something(session, previous_transaction):
if session.is_active:
session.execute("select * from some_table")
:param session: The target :class:`.Session`.
:param previous_transaction: The :class:`.SessionTransaction`
transactional marker object which was just closed. The current
:class:`.SessionTransaction` for the given :class:`.Session` is
available via the :attr:`.Session.transaction` attribute.
.. versionadded:: 0.7.3
"""
def listens_for(target, identifier, *args, **kw):
"""Decorate a function as a listener for the given target + identifier.
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`.
.. seealso::
:func:`.listen` - general description of event listening
"""
def decorate(fn):
listen(target, identifier, fn, *args, **kw)
return fn
return decorate
def before_execute(self, conn, clauseelement, multiparams, params):
"""Intercept high level execute() events, receiving uncompiled
SQL constructs and other objects prior to rendering into SQL.
This event is good for debugging SQL compilation issues as well
as early manipulation of the parameters being sent to the database,
as the parameter lists will be in a consistent format here.
This event can be optionally established with the ``retval=True``
flag. The ``clauseelement``, ``multiparams``, and ``params``
arguments should be returned as a three-tuple in this case::
@event.listens_for(Engine, "before_execute", retval=True)
def before_execute(conn, conn, clauseelement, multiparams, params):
# do something with clauseelement, multiparams, params
return clauseelement, multiparams, params
:param conn: :class:`.Connection` object
:param clauseelement: SQL expression construct, :class:`.Compiled`
instance, or string statement passed to :meth:`.Connection.execute`.
:param multiparams: Multiple parameter sets, a list of dictionaries.
:param params: Single parameter set, a single dictionary.
See also:
:meth:`.before_cursor_execute`
"""
def before_cursor_execute(self, conn, cursor, statement,
parameters, context, executemany):
"""Intercept low-level cursor execute() events before execution,
receiving the string SQL statement and DBAPI-specific parameter list to
be invoked against a cursor.
This event is a good choice for logging as well as late modifications
to the SQL string. It's less ideal for parameter modifications except
for those which are specific to a target backend.
This event can be optionally established with the ``retval=True``
flag. The ``statement`` and ``parameters`` arguments should be
returned as a two-tuple in this case::
@event.listens_for(Engine, "before_cursor_execute", retval=True)
def before_cursor_execute(conn, cursor, statement,
parameters, context, executemany):
# do something with statement, parameters
return statement, parameters
See the example at :class:`.ConnectionEvents`.
:param conn: :class:`.Connection` object
:param cursor: DBAPI cursor object
:param statement: string SQL statement, as to be passed to the DBAPI
:param parameters: Dictionary, tuple, or list of parameters being
passed to the ``execute()`` or ``executemany()`` method of the
DBAPI ``cursor``. In some cases may be ``None``.
:param context: :class:`.ExecutionContext` object in use. May
be ``None``.
:param executemany: boolean, if ``True``, this is an ``executemany()``
call, if ``False``, this is an ``execute()`` call.
See also:
:meth:`.before_execute`
:meth:`.after_cursor_execute`
"""
def _sqlite_post_configure_engine(url, engine, follower_ident):
from sqlalchemy import event
@event.listens_for(engine, "connect")
def connect(dbapi_connection, connection_record):
# use file DBs in all cases, memory acts kind of strangely
# as an attached
if not follower_ident:
dbapi_connection.execute(
'ATTACH DATABASE "test_schema.db" AS test_schema')
else:
dbapi_connection.execute(
'ATTACH DATABASE "%s_test_schema.db" AS test_schema'
% follower_ident)
def after_soft_rollback(self, session, previous_transaction):
"""Execute after any rollback has occurred, including "soft"
rollbacks that don't actually emit at the DBAPI level.
This corresponds to both nested and outer rollbacks, i.e.
the innermost rollback that calls the DBAPI's
rollback() method, as well as the enclosing rollback
calls that only pop themselves from the transaction stack.
The given :class:`.Session` can be used to invoke SQL and
:meth:`.Session.query` operations after an outermost rollback
by first checking the :attr:`.Session.is_active` flag::
@event.listens_for(Session, "after_soft_rollback")
def do_something(session, previous_transaction):
if session.is_active:
session.execute("select * from some_table")
:param session: The target :class:`.Session`.
:param previous_transaction: The :class:`.SessionTransaction`
transactional marker object which was just closed. The current
:class:`.SessionTransaction` for the given :class:`.Session` is
available via the :attr:`.Session.transaction` attribute.
.. versionadded:: 0.7.3
"""
def listens_for(target, identifier, *args, **kw):
"""Decorate a function as a listener for the given target + identifier.
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`.
.. seealso::
:func:`.listen` - general description of event listening
"""
def decorate(fn):
listen(target, identifier, fn, *args, **kw)
return fn
return decorate
def before_execute(self, conn, clauseelement, multiparams, params):
"""Intercept high level execute() events, receiving uncompiled
SQL constructs and other objects prior to rendering into SQL.
This event is good for debugging SQL compilation issues as well
as early manipulation of the parameters being sent to the database,
as the parameter lists will be in a consistent format here.
This event can be optionally established with the ``retval=True``
flag. The ``clauseelement``, ``multiparams``, and ``params``
arguments should be returned as a three-tuple in this case::
@event.listens_for(Engine, "before_execute", retval=True)
def before_execute(conn, conn, clauseelement, multiparams, params):
# do something with clauseelement, multiparams, params
return clauseelement, multiparams, params
:param conn: :class:`.Connection` object
:param clauseelement: SQL expression construct, :class:`.Compiled`
instance, or string statement passed to :meth:`.Connection.execute`.
:param multiparams: Multiple parameter sets, a list of dictionaries.
:param params: Single parameter set, a single dictionary.
See also:
:meth:`.before_cursor_execute`
"""
def before_cursor_execute(self, conn, cursor, statement,
parameters, context, executemany):
"""Intercept low-level cursor execute() events before execution,
receiving the string SQL statement and DBAPI-specific parameter list to
be invoked against a cursor.
This event is a good choice for logging as well as late modifications
to the SQL string. It's less ideal for parameter modifications except
for those which are specific to a target backend.
This event can be optionally established with the ``retval=True``
flag. The ``statement`` and ``parameters`` arguments should be
returned as a two-tuple in this case::
@event.listens_for(Engine, "before_cursor_execute", retval=True)
def before_cursor_execute(conn, cursor, statement,
parameters, context, executemany):
# do something with statement, parameters
return statement, parameters
See the example at :class:`.ConnectionEvents`.
:param conn: :class:`.Connection` object
:param cursor: DBAPI cursor object
:param statement: string SQL statement, as to be passed to the DBAPI
:param parameters: Dictionary, tuple, or list of parameters being
passed to the ``execute()`` or ``executemany()`` method of the
DBAPI ``cursor``. In some cases may be ``None``.
:param context: :class:`.ExecutionContext` object in use. May
be ``None``.
:param executemany: boolean, if ``True``, this is an ``executemany()``
call, if ``False``, this is an ``execute()`` call.
See also:
:meth:`.before_execute`
:meth:`.after_cursor_execute`
"""
def _sqlite_post_configure_engine(url, engine, follower_ident):
from sqlalchemy import event
@event.listens_for(engine, "connect")
def connect(dbapi_connection, connection_record):
# use file DBs in all cases, memory acts kind of strangely
# as an attached
if not follower_ident:
dbapi_connection.execute(
'ATTACH DATABASE "test_schema.db" AS test_schema')
else:
dbapi_connection.execute(
'ATTACH DATABASE "%s_test_schema.db" AS test_schema'
% follower_ident)
