[Python-Dev] Change to PyIter_Next()?

[Tim Peters]

[Tim]
>> In spare moments, I've been plugging away at ... iterators

[Guido]
> For which efforts I extend my greatest thanks!

Yet but a pale reflection of the thanks I extend to you for implementing
these guys to begin with:  they're *loads* of fun!  But not nearly as much
fun as playing with Perl, so they're still prudently Pythonic <wink>.

[T proposed adding a int* error arg to PyIter_Next()]

[G]
> How about making PyIter_Next() call PyErr_Clear() when the exception
> is StopIteration?
>
> Then calls could be
>
>     op2 = PyIter_Next(it);
>     if (op2 == NULL) {
>         if (PyErr_Occurred())
>             goto Fail;
>         break;
>     }

Perfect.  I'll do that later tonight, and update the PEP to match.

> This is a tad slower and arguably generates more code (assuming an
> extra call is slower than passing an extra argument and loading it)
> but doesn't require declaring the error variable.

Well, it's two more calls (since PyErr_Occurred() also makes a call to get
the thread state), but I don't really care because the client only does this
in case of error or end-of-iteration (which aren't the normal cases).  I was
dreading finding a spare int var to pass inside FOR_ITER anyway <wink>.