python subclassing: TypeError object.new() takes no parameters

Question

Ok I'm stumped again! This should be easy though ;-)

I'm trying to subclass the pytables class tables.IsDefinition, as follows:

import tables

class doc(tables.IsDescription):
    def __init__(self, data):
        self.data = data

And then I try to instantiate it I get an error:

doc('test')

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)

...<ipython console> in <module>()

TypeError: object.__new__() takes no parameters

This is with Python 2.6.5 (r265:79063, Apr 16 2010, 13:57:41) and IPython 0.10

What am I doing wrong?

I don't know PyTables, but from quick Google search it seems `IsDescription` is a metaclass, not a class. — Cat Plus Plus, Jan 05 '12 at 11:13
Ah ok ... the manual doesn't make that clear. Thanks for the pointer — tdc, Jan 05 '12 at 11:30
@CatPlusPlus It looks like you should post your comment as an answer so that it can be accepted. — jcollado, Jan 07 '12 at 05:22

score 2 · Accepted Answer · edited May 23 '17 at 10:24

2

In case anyone else lands here, the answer is that IsDescription is a "metaclass". More information can be found on this thread

edited May 23 '17 at 10:24

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answered Jan 17 '12 at 13:10

tdc

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python subclassing: TypeError object.new() takes no parameters

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python subclassing: TypeError object.__new__() takes no parameters

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python subclassing: TypeError object.new() takes no parameters