Classe « ColumnDefault »

Constructeur sqlalchemy.ColumnDefault.__init__

Signature de la constructeur __init__

def __init__(self, arg, **kwargs) 

Description

__init__.__doc__

Construct a new :class:`.ColumnDefault`.


        :param 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
           :class:`_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 :class:`.ExecutionContext`,
           which provides contextual information as to the current
           :class:`_engine.Connection` in use as well as the current
           statement and parameters.