How Can I Efficiently Iterate Over Overlapping Pairs in Python Lists?

Sliding Window Technique for Iterating Over Overlapping Pairs

When working with lists in Python, it is often necessary to iterate over overlapping pairs of elements. A common approach is to use zip and zip[1:] to create two iterators that advance independently over the list. However, there may be more efficient or idiomatic ways to achieve the same result.

Itertools Pairwise Function

Python 3.8 introduces the pairwise function from the itertools module. This function takes an iterable and returns an iterator that yields overlapping pairs of elements.

For Python versions below 3.8, a similar function can be implemented using tee:

def pairwise(iterable):
    "s -> (s0, s1), (s1, s2), (s2, s3), ..."
    a, b = itertools.tee(iterable)
    next(b, None)
    return zip(a, b)

Benefits of Pairwise

The pairwise function has several advantages over the traditional zip approach:

• It only creates two iterators, whereas the zip approach creates three.
• It can be easily adapted to produce sliding windows of any size using the tee function's n parameter.
• It is a built-in function and therefore more efficient than a custom implementation.

Conclusion

While the traditional zip approach is functional, the pairwise function provides a more efficient and idiomatic way to iterate over overlapping pairs of elements in Python. It is particularly useful for creating sliding windows of data for processing or analysis.

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