Subclassing cElementTree.Element

[Kent Johnson]

Is it possible to subclass cElementTree.El ement? I tried[color=blue][color=green][color=darkred]
>>> import cElementTree as et
>>> class Elt(et.Element) :[/color][/color][/color]
... pass
...
Traceback (most recent call last):
File "<stdin>", line 1, in ?
TypeError: Error when calling the metaclass bases
cannot create 'builtin_functi on_or_method' instances

I want to create a tree where I can navigate from a node to its parent. The standard Element class
doesn't seem to support this so I am trying to make a subclass that does. The XML files in question
are large so the speed of cElementTree is very helpful.

Thanks,
Kent

(apologies if this is a duplicate post)

[Fredrik Lundh]

Re: Subclassing cElementTree.El ement

Kent Johnson wrote:
[color=blue]
> Is it possible to subclass cElementTree.El ement? I tried[color=green][color=darkred]
> >>> import cElementTree as et
> >>> class Elt(et.Element) :[/color][/color]
> ... pass
> ...
> Traceback (most recent call last):
> File "<stdin>", line 1, in ?
> TypeError: Error when calling the metaclass bases
> cannot create 'builtin_functi on_or_method' instances[/color]

Nope.

This is by design; Elements are intended to be contained, not subclassed. (you
cannot subclass ElementTree Elements either; Element is a factory function, not
a class).

To solve the navigation issue, you could either use a dictionary that keeps track
of child-parent relations, or use a proxy wrapper. Or see if you can structure your
code so you always work from parents (that's usually easier than you may think).

</F>