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- import abc
- from ..util import ABC
- class ConnectionCharacteristic(ABC):
- """An abstract base for an object that can set, get and reset a
- per-connection characteristic, typically one that gets reset when the
- connection is returned to the connection pool.
- transaction isolation is the canonical example, and the
- ``IsolationLevelCharacteristic`` implementation provides this for the
- ``DefaultDialect``.
- The ``ConnectionCharacteristic`` class should call upon the ``Dialect`` for
- the implementation of each method. The object exists strictly to serve as
- a dialect visitor that can be placed into the
- ``DefaultDialect.connection_characteristics`` dictionary where it will take
- effect for calls to :meth:`_engine.Connection.execution_options` and
- related APIs.
- .. versionadded:: 1.4
- """
- __slots__ = ()
- transactional = False
- @abc.abstractmethod
- def reset_characteristic(self, dialect, dbapi_conn):
- """Reset the characteristic on the connection to its default value."""
- @abc.abstractmethod
- def set_characteristic(self, dialect, dbapi_conn, value):
- """set characteristic on the connection to a given value."""
- @abc.abstractmethod
- def get_characteristic(self, dialect, dbapi_conn):
- """Given a DBAPI connection, get the current value of the
- characteristic.
- """
- class IsolationLevelCharacteristic(ConnectionCharacteristic):
- transactional = True
- def reset_characteristic(self, dialect, dbapi_conn):
- dialect.reset_isolation_level(dbapi_conn)
- def set_characteristic(self, dialect, dbapi_conn, value):
- dialect.set_isolation_level(dbapi_conn, value)
- def get_characteristic(self, dialect, dbapi_conn):
- return dialect.get_isolation_level(dbapi_conn)
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