[Python-Dev] folding cElementTree behind ElementTree in 3.3 (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Mon Feb 20 23:51:34 CET 2012

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

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