How to tell the difference between an iterator and an iterable?

Question

In Python the interface of an iterable is a subset of the iterator interface. This has the advantage that in many cases they can be treated in the same way. However, there is an

Answer 1

import itertools

def process(iterable):
    work_iter, backup_iter= itertools.tee(iterable)

    for item in work_iter:
        # bla bla
        if need_to_startover():
            for another_item in backup_iter:

That damn time machine that Raymond borrowed from Guido…