Release: 1.2.19 | Release Date: April 15, 2019

# SQLAlchemy 1.2 Documentation

# Core Exceptions

Exceptions used with SQLAlchemy.

The base exception class is `SQLAlchemyError`. Exceptions which are raised as a result of DBAPI exceptions are all subclasses of `DBAPIError`.

exception `sqlalchemy.exc.``AmbiguousForeignKeysError`(*arg, **kw)

  Raised when more than one foreign key matching can be located between two selectables during a join.

exception `sqlalchemy.exc.``ArgumentError`(*arg, **kw)

  Raised when an invalid or conflicting function argument is supplied.

  This error generally corresponds to construction time state errors.

exception `sqlalchemy.exc.``CircularDependencyError`(message, cycles, edges, msg=None, code=None)

  Raised by topological sorts when a circular dependency is detected.

  There are two scenarios where this error occurs:

  - In a Session flush operation, if two objects are mutually dependent on each other, they can not be inserted or deleted via INSERT or DELETE statements alone; an UPDATE will be needed to post-associate or pre-deassociate one of the foreign key constrained values. The `post_update` flag described at Rows that point to themselves / Mutually Dependent Rows can resolve this cycle.

  - In a `MetaData.sorted_tables` operation, two `ForeignKey` or `ForeignKeyConstraint` objects mutually refer to each other. Apply the `use_alter=True` flag to one or both, see Creating/Dropping Foreign Key Constraints via ALTER.

exception `sqlalchemy.exc.``CompileError`(*arg, **kw)

  Raised when an error occurs during SQL compilation

exception `sqlalchemy.exc.``DBAPIError`(statement, params, orig, connection_invalidated=False, code=None)

  Raised when the execution of a database operation fails.

  Wraps exceptions raised by the DB-API underlying the database operation. Driver-specific implementations of the standard DB-API exception types are wrapped by matching sub-types of SQLAlchemy’s `DBAPIError` when possible. DB-API’s `Error` type maps to `DBAPIError` in SQLAlchemy, otherwise the names are identical. Note that there is no guarantee that different DB-API implementations will raise the same exception type for any given error condition.

  `DBAPIError` features `statement` and `params` attributes which supply context regarding the specifics of the statement which had an issue, for the typical case when the error was raised within the context of emitting a SQL statement.

  The wrapped exception object is available in the `orig` attribute. Its type and properties are DB-API implementation specific.

exception `sqlalchemy.exc.``DataError`(statement, params, orig, connection_invalidated=False, code=None)

  Wraps a DB-API DataError.

exception `sqlalchemy.exc.``DatabaseError`(statement, params, orig, connection_invalidated=False, code=None)

  Wraps a DB-API DatabaseError.

exception `sqlalchemy.exc.``DisconnectionError`(*arg, **kw)

  A disconnect is detected on a raw DB-API connection.

  This error is raised and consumed internally by a connection pool. It can be raised by the `PoolEvents.checkout()` event so that the host pool forces a retry; the exception will be caught three times in a row before the pool gives up and raises `InvalidRequestError` regarding the connection attempt.

class `sqlalchemy.exc.``DontWrapMixin`

  A mixin class which, when applied to a user-defined Exception class, will not be wrapped inside of `StatementError` if the error is emitted within the process of executing a statement.

  E.g.:

      from sqlalchemy.exc import DontWrapMixin

      class MyCustomException(Exception, DontWrapMixin):
          pass

      class MySpecialType(TypeDecorator):
          impl = String

          def process_bind_param(self, value, dialect):
              if value == 'invalid':
                  raise MyCustomException("invalid!")

exception `sqlalchemy.exc.``IdentifierError`(*arg, **kw)

  Raised when a schema name is beyond the max character limit

exception `sqlalchemy.exc.``IntegrityError`(statement, params, orig, connection_invalidated=False, code=None)

  Wraps a DB-API IntegrityError.

exception `sqlalchemy.exc.``InterfaceError`(statement, params, orig, connection_invalidated=False, code=None)

  Wraps a DB-API InterfaceError.

exception `sqlalchemy.exc.``InternalError`(statement, params, orig, connection_invalidated=False, code=None)

  Wraps a DB-API InternalError.

exception `sqlalchemy.exc.``InvalidRequestError`(*arg, **kw)

  SQLAlchemy was asked to do something it can’t do.

  This error generally corresponds to runtime state errors.

exception `sqlalchemy.exc.``InvalidatePoolError`(*arg, **kw)

  Raised when the connection pool should invalidate all stale connections.

  A subclass of `DisconnectionError` that indicates that the disconnect situation encountered on the connection probably means the entire pool should be invalidated, as the database has been restarted.

  This exception will be handled otherwise the same way as `DisconnectionError`, allowing three attempts to reconnect before giving up.

  New in version 1.2.

exception `sqlalchemy.exc.``NoForeignKeysError`(*arg, **kw)

  Raised when no foreign keys can be located between two selectables during a join.

exception `sqlalchemy.exc.``NoInspectionAvailable`(*arg, **kw)

  A subject passed to `sqlalchemy.inspection.inspect()` produced no context for inspection.

exception `sqlalchemy.exc.``NoReferenceError`(*arg, **kw)

  Raised by `ForeignKey` to indicate a reference cannot be resolved.

exception `sqlalchemy.exc.``NoReferencedColumnError`(message, tname, cname)

  Raised by `ForeignKey` when the referred `Column` cannot be located.

exception `sqlalchemy.exc.``NoReferencedTableError`(message, tname)

  Raised by `ForeignKey` when the referred `Table` cannot be located.

exception `sqlalchemy.exc.``NoSuchColumnError`

  A nonexistent column is requested from a `RowProxy`.

exception `sqlalchemy.exc.``NoSuchModuleError`(*arg, **kw)

  Raised when a dynamically-loaded module (usually a database dialect) of a particular name cannot be located.

exception `sqlalchemy.exc.``NoSuchTableError`(*arg, **kw)

  Table does not exist or is not visible to a connection.

exception `sqlalchemy.exc.``NotSupportedError`(statement, params, orig, connection_invalidated=False, code=None)

  Wraps a DB-API NotSupportedError.

exception `sqlalchemy.exc.``ObjectNotExecutableError`(target)

  Raised when an object is passed to .execute() that can’t be executed as SQL.

  New in version 1.1.

exception `sqlalchemy.exc.``OperationalError`(statement, params, orig, connection_invalidated=False, code=None)

  Wraps a DB-API OperationalError.

exception `sqlalchemy.exc.``ProgrammingError`(statement, params, orig, connection_invalidated=False, code=None)

  Wraps a DB-API ProgrammingError.

exception `sqlalchemy.exc.``ResourceClosedError`(*arg, **kw)

  An operation was requested from a connection, cursor, or other object that’s in a closed state.

exception `sqlalchemy.exc.``SADeprecationWarning`

  Issued once per usage of a deprecated API.

exception `sqlalchemy.exc.``SAPendingDeprecationWarning`

  Issued once per usage of a deprecated API.

exception `sqlalchemy.exc.``SAWarning`

  Issued at runtime.

exception `sqlalchemy.exc.``SQLAlchemyError`(*arg, **kw)

  Generic error class.

exception `sqlalchemy.exc.``StatementError`(message, statement, params, orig, code=None)

  An error occurred during execution of a SQL statement.

  `StatementError` wraps the exception raised during execution, and features `statement` and `params` attributes which supply context regarding the specifics of the statement which had an issue.

  The wrapped exception object is available in the `orig` attribute.

  `orig` = None

    The DBAPI exception object.

  `params` = None

    The parameter list being used when this exception occurred.

  `statement` = None

    The string SQL statement being invoked when this exception occurred.

exception `sqlalchemy.exc.``TimeoutError`(*arg, **kw)

  Raised when a connection pool times out on getting a connection.

exception `sqlalchemy.exc.``UnboundExecutionError`(*arg, **kw)

  SQL was attempted without a database connection to execute it on.

exception `sqlalchemy.exc.``UnreflectableTableError`(*arg, **kw)

  Table exists but can’t be reflected for some reason.

  New in version 1.2.

exception `sqlalchemy.exc.``UnsupportedCompilationError`(compiler, element_type)

  Raised when an operation is not supported by the given compiler.

  See also

  How do I render SQL expressions as strings, possibly with bound parameters inlined?

  Compiler StrSQLCompiler can’t render element of type <element type>