[Python-Dev] Very Strange Argument Handling Behavior

[Dino Viehland]

Maciej wrote:
> On Sat, Apr 17, 2010 at 11:38 AM, Dino Viehland <dinov at microsoft.com>
> wrote:
> > Benjamin wrote:
> >> 2010/4/17 Guido van Rossum <guido at python.org>:
> >> > On Sat, Apr 17, 2010 at 9:22 AM, Nick Coghlan <ncoghlan at gmail.com>
> >> wrote:
> >> >> Guido van Rossum wrote:
> >> >>> Because Python promises that the object the callee sees as
> 'kwargs'
> >> is
> >> >>> "just a dict".
> >> >>
> >> >> Huh, I thought kwargs was allowed to be implemented as a
> >> >> string-keys-only dict (similar to class and module namespaces)
> while
> >> >> still be a valid Python implementation. I guess I was wrong.
> >> >
> >> > Actually I don't know about that. Is there language anywhere in
> the
> >> > language reference that says this? What do IronPython, Jython,
> PyPy
> >> > actually do?
> >>
> >> Similar to CPython, PyPy has dict versions optimized for strings,
> >> which fall back to the general version when given non-string keys.
> >
> > IronPython as well.  The only place we use a string only dict is for
> > new-style classes whose dict's are wrapped in a dictproxy.
> 
> And yet that breaks some code :-)

Sure, if you do:

class C(object):
    locals()[object()] = 42

dir(C)

You lose.  Once I'm aware of some piece of code in the wild doing this
then I'll be happy to change IronPython to be more compatible. :)