gistfile1.py

from itertools import chain

def istail(it):
    '''Check if iterator has one more element. Return True/False and
    iterator.'''
    try:
        i = next(it)
    except StopIteration:
        return False, it

    try:
        j = next(it)
        return False, chain([i, j], it)
    except StopIteration:
        return True, chain([i], it)


t, it = istail(iter([]))
print t, list(it)
t, it = istail(iter([1]))
print t, list(it)
t, it = istail(iter([1, 2]))
print t, list(it)