On 9/20/05, Terry Reedy <tjreedy@udel.edu> wrote:
I presume there were two reasons: internal efficiency of preallocations (list(some_it) for example)
This could have been implemented without making the implementation details public.
and letting people differentiate iterator with something left to return versus nothing, just as we can differentiate collections with something versus nothing.
But this is against the very idea of the iterator protocol -- for general iterators, there may be no way to determine whether there is a next item without actually producing the item, so the proper approach is to code with that in mind. When this type of look-ahead is required, a buffering iterator should be inserted, so that the algorithm can work with all iterators rather than only with iterators over built-in containers. -- --Guido van Rossum (home page: http://www.python.org/~guido/)