[Python-Dev] Raising assertions on wrong element types in ElementTree

[R. David Murray]

On Fri, 16 Mar 2012 15:49:33 -0400, Terry Reedy <tjreedy at udel.edu> wrote:
> On 3/16/2012 11:33 AM, R. David Murray wrote:
> > On Fri, 16 Mar 2012 09:38:49 +0200, Eli Bendersky<eliben at gmail.com>  wrote:
> >> 1. The behavior of append, insert and extend should be similar in this respect
> >> 2. AssertionError is not the customary error in such case - TypeError
> >> is much more suitable
> >> 3. The C implementation of ElementTree actually raises TypeError in
> >> all these methods, by virtue of using PyArg_ParseTuple
> >> 4. The Python implementation (at least in 3.2) actually doesn't raise
> >> even AssertionError in extend - this was commented out
> 
> > Our usual approach in cases like this is to not change it in the maint
> > releases.  Why risk breaking someone's code for no particular benefit?
> > If you want some extra work you could add it as a deprecation warning,
> > I suppose.
> 
> The deprecation warning would be that ignoring the error is deprecated 
> ;-). I think this would be a good idea since it would only appear when 
> someone is checking for how to change their code for 3.3.

Yes :).  But concretely the deprecation warning is that if anyone has
code that for some reason *works* with the python version of ElementTree
while passing in a non-Element (duck typing?), that will no longer be
allowed in 3.3.  So it does seem worthwhile to do that.

--David