["python","list","iterator"]
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. How can I do this neatly in Python? If you instead need an immediately created list of the results up to a certain length, rather than iterating on demand: see Repeat list to max number of elements for general techniques, and How to replicate array to specific length array for Numpy-specific techniques.
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'