[Python-Dev] folding cElementTree behind ElementTree in 3.3

[Nick Coghlan]

On Tue, Feb 21, 2012 at 1:55 AM,  <martin at v.loewis.de> wrote:
>> Basically, if something is just documented as being callable without
>> subclassing or instance checks being mentioned as supported in the
>> docs, it can be implemented as either a type or an ordinary function,
>> or pretty much any other kind of callable without being deemed an API
>> change
>
>
> So what would be your evaluation of
>
> http://docs.python.org/library/xml.etree.elementtree.html#xml.etree.ElementTree.Element
>
> in that respect?

Completely different from the functools.partial case - with that, the
docs are very careful to *never* call functools.partial a class
(instead saying "returns a callable object").

The ElementTree docs unambiguously call Element a class (several
times), so a conforming implementation must provide it as a class
(i.e. supporting use in isinstance() checks. inheritance, etc) rather
than as just a callable. A factory function is not a backwards
compatible replacement (sorry Eli - given those docs, I'm definitely
with Martin on this one).

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia