How to Iterate Over Circular Lists in Python: Using itertools.cycle for Efficiency

Iterating Circular Lists in Python

Creating an iterator for circular lists, where each iteration starts from the last visited element, is a common programming task. For example, this functionality is useful in managing connection pools, where an iterator checks and returns available connections.

In Python, the itertools.cycle module can efficiently handle this task. It creates an iterator that endlessly loops through a provided sequence:

<code class="python">from itertools import cycle

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

pool = cycle(lst)

for item in pool:
    print(item)</code>

The above code will indefinitely print the elements 'a', 'b', 'c'.

Alternatively, to manually advance the iterator and retrieve values one by one, use the next function:

<code class="python">&gt;&gt;&gt; next(pool)
'a'
&gt;&gt;&gt; next(pool)
'b'</code>

Using itertools.cycle provides a neat and efficient solution for iterating over circular lists in Python.

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