How to Iterate Over Consecutive Pairs of Items in a Python List?

Iterators for Consecutive List Item Pairs

Given a list of elements, you may need to iterate over consecutive pairs of items in the list. While it is possible to use a for loop to iterate through the list one element at a time and manually retrieve the consecutive item, there is a more compact and efficient way to achieve this using Python iterators.

The zip() Function

Python's zip() function is a built-in iterator that allows for the creation of tuples from corresponding elements of multiple iterables. In this case, we can use zip() to create tuples of consecutive list items. For example:

l = [1, 7, 3, 5]

for first, second in zip(l, l[1:]):
    print(first, second)

This code will output:

1 7
7 3
3 5

The zip() function takes two arguments: the first is the original list, and the second is the list with the first element removed (achieved using l[1:]). It then combines corresponding elements into tuples, creating an iterator over these tuples.

Using itertools.izip()

For Python 2 users, the itertools module provides an alternative function called izip(). This function is similar to zip(), but it returns an izip object that can be lazily evaluated and doesn't require the creation of a new list in memory. However, it is recommended to use zip() in Python 3 as it is more efficient and easier to use.

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