[Python-3000] rename it.next() to it.__next__(), add a next() built-in

["Martin v. Löwis"]

Terry Reedy schrieb:
> On the consistency argument: sorted(somelist) calls copy(somelist).sort, 
> not copy(somelist).__sort__.  

Actually, it calls list(somelist).sort, so it requires iteration, not 
copying, and the result will be known to be a list. So the important
difference is that .sort is not a method that the argument to sorted
needs to implement (indeed, it has no option to define its own sorting
algorithm). This is different from __next__, which user-defined types
will need to implement.

> One of the virtues, and as I recall, design purposes, of .next calls is to 
> be fast. 

I think this holds for the C level only. Python-level invocations will 
create a method-wrapper (or bound method) every time, so that won't
be fast.

Regards,
Martin