Sorry, it should've been:
class Enum_Sample(Base):
Typo.
On Mon, Aug 26, 2013 at 4:35 PM, Praveen <praveen.venk...@gmail.com> wrote:
> The problem with using Mixins is that you need to know the definition of
> columns already for creating the mixin class. What I am trying to do is
> more like get the definition dynamically on the fly.Take a look at this:
>
> def get_properties(tablename, map):
> table_inspector = reflection.Inspector.from_engine(DB_ENGINE.connect())
> table = Table(tablename, metadata)
> table_inspector.reflecttable(table, None)
> columns = []
> for child in table.get_children():
> if isinstance(child, Column):
> column = list(child.base_columns)[0]
> column.table = None
> columns.append(column)
> return dict([(map[column.key], column) for column in columns])
>
> class CustomDeclarativeMeta(DeclarativeMeta):
> def __new__(cls, name, bases, attrs):
> attrs.update(get_properties(attrs.get('__tablename__'),
> attrs.get('__map__')))
> return super(CustomDeclarativeMeta, cls).__new__(cls, name, bases,
> attrs)
>
> # Base = declarative_base(metaclass=CustomDeclarativeMeta)
> Base = declarative_base()
>
> class Enum_SampleBase):
> __tablename__ = 'Enum_Sample'
> __table_args__ = {'useexisting': True}
> __metaclass__ = CustomDeclarativeMeta
> __map__ = {'Id': 'id', 'Name': 'name', 'Description': 'description',
> 'IsActive': 'is_active'}
>
> 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)
>
> Unfortunately, this isn't working. I want to declare column types by
> getting them from a table that's already created in the database.
>
>
>
> On Wed, Jul 3, 2013 at 11:11 AM, Michael Bayer
> <mike...@zzzcomputing.com>wrote:
>
>> your metaclass must derive from the DeclarativeMeta class.
>>
>> Also, I disagree that you need this metaclass, what you're trying to do
>> is very easy using mixins, which are supported in version 0.6:
>> http://docs.sqlalchemy.org/en/rel_0_6/orm/extensions/declarative.html#mixing-in-columns
>>
>>
>>
>>
>> On Jul 3, 2013, at 12:44 AM, Ven Karri <praveen.venk...@gmail.com> wrote:
>>
>> I use: Python 2.6 and sqlalchemy 0.6.1
>>
>> This is what I am trying to do:
>>
>> 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:
>>
>> 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
>>
>> Now, if I do the same thing above by using
>>
>> class Sample(object)
>>
>> instead of
>>
>> 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**
>>
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>>
>>
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>>
>
>
>
> --
> Have a nice day !!!
>
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