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POHow to define metaclass for a class that extends from sqlalchemy declarative base
 

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  1. POHow to define metaclass for a class that extends from sqlalchemy declarative base
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    <p>I use: Python 2.6 and sqlalchemy 0.6.1</p> <p>This is what I am trying to do:</p> <pre><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 "&lt;(%d, '%s', '%s', %r)&gt;" % (self.id, self.name, self.description, self.isactive) </code></pre> <p>And the error I am getting is this:</p> <pre><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 bases </code></pre> <p>Now, if I do the same thing above by using</p> <pre><code>class Sample(object) </code></pre> <p>instead of</p> <pre><code>class Sample(Base) </code></pre> <p>it works absolutely fine.</p> <p>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.</p> <p><strong>Please help</strong> </p>
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