sqlalchemy.sql.schema.ColumnDefault

class documentation

class ColumnDefault(DefaultGenerator):

A plain default value on a column.

This could correspond to a constant, a callable function, or a SQL clause.

.ColumnDefault is generated automatically whenever the default, onupdate arguments of _schema.Column are used. A .ColumnDefault can be passed positionally as well.

For example, the following:

Column('foo', Integer, default=50)

Is equivalent to:

Column('foo', Integer, ColumnDefault(50))

Method	`__init__`	Construct a new `.ColumnDefault`.
Method	`__repr__`	Undocumented
Method	`_maybe_wrap_callable`	Wrap callables that don't accept a context.
Instance Variable	`arg`	Undocumented
Property	`_arg_is_typed`	Undocumented
Property	`is_callable`	Undocumented
Property	`is_clause_element`	Undocumented
Property	`is_scalar`	Undocumented

Inherited from DefaultGenerator:

Method	`_execute_on_connection`	Undocumented
Method	`_set_parent`	Associate with this SchemaEvent's parent object.
Method	`execute`	Compile and execute this `.Executable`.
Class Variable	`__visit_name__`	Undocumented
Class Variable	`is_sequence`	Undocumented
Class Variable	`is_server_default`	Undocumented
Instance Variable	`column`	Undocumented
Instance Variable	`for_update`	Undocumented
Property	`bind`	Return the connectable associated with this default.

Inherited from Executable (via DefaultGenerator):

Method	`_add_context_option`	Add a context option to this statement.
Method	`_set_compile_options`	Assign the compile options to a new value.
Method	`_update_compile_options`	update the _compile_options with new keys.
Method	`execution_options`	Set non-SQL options for the statement which take effect during execution.
Method	`get_execution_options`	Get the non-SQL options which will take effect during execution.
Method	`options`	Apply options to this statement.
Method	`scalar`	Compile and execute this `.Executable`, returning the result's scalar representation.
Class Variable	`_bind`	Undocumented
Class Variable	`_executable_traverse_internals`	Undocumented
Class Variable	`_with_context_options`	Undocumented
Class Variable	`_with_options`	Undocumented
Class Variable	`is_delete`	Undocumented
Class Variable	`is_dml`	Undocumented
Class Variable	`is_insert`	Undocumented
Class Variable	`is_select`	Undocumented
Class Variable	`is_text`	Undocumented
Class Variable	`is_update`	Undocumented
Class Variable	`supports_execution`	Undocumented
Instance Variable	`_compile_options`	Undocumented
Instance Variable	`_execution_options`	Undocumented
Property	`_effective_plugin_target`	Undocumented

Inherited from StatementRole (via DefaultGenerator, Executable):

Class Variable	`_propagate_attrs`	Undocumented
Class Variable	`_role_name`	Undocumented

Inherited from SQLRole (via DefaultGenerator, Executable, StatementRole):

Class Variable	`allows_lambda`	Undocumented
Class Variable	`uses_inspection`	Undocumented

Inherited from Generative (via DefaultGenerator, Executable):

Method _generate Undocumented

Inherited from SchemaItem (via DefaultGenerator):

Method	`_init_items`	Initialize the list of child items for this SchemaItem.
Method	`_schema_item_copy`	Undocumented
Class Variable	`_use_schema_map`	Undocumented
Class Variable	`create_drop_stringify_dialect`	Undocumented
Property	`info`	Info dictionary associated with the object, allowing user-defined data to be associated with this `.SchemaItem`.

Inherited from SchemaEventTarget (via DefaultGenerator, SchemaItem):

Method _set_parent_with_dispatch Undocumented

Inherited from Traversible (via DefaultGenerator, SchemaItem):

Method	`get_children`	Return immediate child `.visitors.Traversible` elements of this `.visitors.Traversible`.
Method	`__class_getitem__`	Undocumented

def __init__(self, arg, **kwargs):

overrides sqlalchemy.sql.schema.DefaultGenerator.__init__

Construct a new .ColumnDefault.

Parameters

arg

argument representing the default value. May be one of the following:

a plain non-callable Python value, such as a string, integer, boolean, or other simple type. The default value will be used as is each time.
a SQL expression, that is one which derives from _expression.ColumnElement. The SQL expression will be rendered into the INSERT or UPDATE statement, or in the case of a primary key column when RETURNING is not used may be pre-executed before an INSERT within a SELECT.
A Python callable. The function will be invoked for each new row subject to an INSERT or UPDATE. The callable must accept exactly zero or one positional arguments. The one-argument form will receive an instance of the .ExecutionContext, which provides contextual information as to the current _engine.Connection in use as well as the current statement and parameters.

**kwargs Undocumented

def __repr__(self):

overrides sqlalchemy.sql.schema.SchemaItem.__repr__

Undocumented

def _maybe_wrap_callable(self, fn):

Wrap callables that don't accept a context.

This is to allow easy compatibility with default callables that aren't specific to accepting of a context.

arg =

Undocumented

@util.memoized_property
@util.preload_module('sqlalchemy.sql.sqltypes')
_arg_is_typed =

Undocumented

@util.memoized_property
is_callable =

Undocumented

@util.memoized_property
is_clause_element =

Undocumented

@util.memoized_property
is_scalar =

Undocumented