[Python-Dev] Very Strange Argument Handling Behavior

[Dino Viehland]

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.