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+---- Thread: How to define metaclass for a class that extends from sqlalc (/showthread.php?tid=27955)
How to define metaclass for a class that extends from sqlalc - imperialguy - 07-02-2013
I use: Python 2.6 and sqlalchemy 0.6.1
This is what I am trying to do:
Code:
from sqlalchemy.types import (
Integer,
String,
Boolean
)
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class SampleMeta(type):
def __new__(cls, name, bases, attrs):
attrs.update({ 'id': Column('Id', Integer, primary_key=True),
'name': Column('Name', String),
'description': Column('Description', String),
'is_active': Column('IsActive', Boolean)
})
return super(SampleMeta, cls).__new__(cls, name, bases, attrs)
class Sample(Base):
__tablename__ = 'Sample'
__table_args__ = {'useexisting': True}
__metaclass__ = SampleMeta
def __init__(self, id, name, description, is_active):
self.id = id
self.name = name
self.description = description
self.is_active = is_active
def __repr__(self):
return "<(%d, '%s', '%s', %r)>" % (self.id, self.name, self.description, self.isactive)And the error I am getting is this:
Code:
TypeError: Error when calling the metaclass bases
metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its basesCode:
class Sample(object)instead of
Code:
class Sample(Base)it works absolutely fine.
I need to update the attributes of the class dynamically. So, I will be using dynamic attribute and column names. And I need the above piece code to work in order to be able to get there.
Please help[/code]