Circular list iterator in Python

I need to iterate over a circular list, possibly many times, each time starting with the last visited item.

The use case is a connection pool. A client asks for connection, an iterator checks if pointed-to connection is available and returns it, otherwise loops until it finds one that is available.

Is there a neat way to do it in Python?

Use itertools.cycle, that's its exact purpose:

    from itertools import cycle

    lst = ['a', 'b', 'c']

    pool = cycle(lst)

    for item in pool:
        print item,

Output:

    a b c a b c ...

(Loops forever, obviously)

In order to manually advance the iterator and pull values from it one by one, simply call next(pool):

    >>> next(pool)
    'a'
    >>> next(pool)
    'b'

From: stackoverflow.com/q/23416381