[Python-Dev] os.path.walk() lacks 'depth first' option

[Guido van Rossum]

> How odd.  I was going to say the reverse; that I *always* want to 
> distinguish between the two, because TypeError almost invariably is a 
> programming error of some kind, while AttributeError is nearly always an 
> error that I'm checking in order to have a fallback.  E.g.:
> 
> try:
>     foo = thingy.foo
> except AttributeError:
>     # default case
> else:
>     foo()
> 
> However, if 'thingy.foo' were to raise any other kind of error, such as a 
> TypeError, it'd probably mean that thingy had a broken 'foo' descriptor 
> that I'd want to know about.

This sounds like a much more advanced use, typical to a certain style
of programming. Others would do this using hasattr() or three-argument
getattr(); some will argue that you should have a base class that
handles the default case so you don't need to handle that case
separately at all (though that may not always be possible, e.g. when
dealing with objects created by a 3rd party library).

Your example argues for allowing to distringuish between
AttributeError and TypeError, but doesn't convince me that they are
totally different beasts.

--Guido van Rossum (home page: http://www.python.org/~guido/)