[Python-Dev] defaultdict and on_missing()

Guido van Rossum guido at python.org
Tue Feb 28 18:02:55 CET 2006

On 2/28/06, Nick Coghlan <ncoghlan at gmail.com> wrote:
> Greg Ewing wrote:
> > Nick Coghlan wrote:
> >
> >> I wouldn't mind seeing one of the early ideas from PEP 340 being
> >> resurrected some day, such that the signature for the special method
> >> was "__next__(self, input)" and for the builtin "next(iterator,
> >> input=None)"
> >
> > Aren't we getting an argument to next() anyway?
> > Or was that idea dropped?
> PEP 342 opted to extend the generator API instead (using "send") and leave the
> iterator protocol alone for the time being.

One of the main reasons for this was the backwards compatibility
problems at the C level. The C implementation doesn't take an
argument. Adding an argument would cause all sorts of code breakage
and possible segfaults (if there's 3rd party code calling tp_next for

In 3.0 we could fix this.

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

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