How to create and pre-populate a not null column in odoo.

gistfile1.py

def _auto_init(self, cr, context):
    """Fill in the required consignee column with default values.

    This is similar to the solution used in mail_alias.py in the core.

    The installation of the module will succeed with no errors, and the
    column will be required immediately (the previous solution made it
    required only on the first module update after installation).

    """

    # create the column non required
    self._columns['consignee_id'].required = False
    super(SaleOrder, self)._auto_init(cr, context=context)

    # fill in the empty records
    no_consignee_ids = self.search(cr, SUPERUSER_ID, [
        ('consignee_id', '=', False)
    ], context=context)
    self.write(cr, SUPERUSER_ID, no_consignee_ids,
                {'consignee_id': SUPERUSER_ID}, context)

    # make the column required again
    self._columns['consignee_id'].required = True
    super(SaleOrder, self)._auto_init(cr, context=context)