Subclassing cElementTree.Element

[Fredrik Lundh]

Kent Johnson wrote:

> Is it possible to subclass cElementTree.Element? I tried
>  >>> import cElementTree as et
>  >>> class Elt(et.Element):
>  ...   pass
>  ...
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: Error when calling the metaclass bases
>     cannot create 'builtin_function_or_method' instances

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).

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