Python | Pair iteration in list

Python | Pair iteration in list

In this tutorial, we'll explore different ways to iterate over pairs of elements in a list. Pair iteration can be especially handy when comparing consecutive elements or when you want to process two elements at once.

Objective:

For a given list:

lst = [1, 2, 3, 4]

We'll explore ways to iterate over the pairs:

(1, 2), (2, 3), (3, 4)

1. Using zip:

The zip function can be used to pair elements of multiple lists. By pairing the list with a version of itself shifted by one position, we can obtain the desired pairs.

lst = [1, 2, 3, 4] for a, b in zip(lst, lst[1:]): print(a, b)

2. Using List Comprehension:

If you want to create a new list of pairs, you can use a list comprehension.

lst = [1, 2, 3, 4] pairs = [(lst[i], lst[i+1]) for i in range(len(lst)-1)] print(pairs) # Output: [(1, 2), (2, 3), (3, 4)]

3. Using enumerate:

enumerate can give you both the index and the value, which can be useful to access the next element.

lst = [1, 2, 3, 4] for i, value in enumerate(lst[:-1]): print(value, lst[i+1])

4. Using a Loop with Indices:

A traditional for loop with indices can be used to access pairs of consecutive elements.

lst = [1, 2, 3, 4] for i in range(len(lst) - 1): print(lst[i], lst[i+1])

Considerations:

  • When working with pair iteration, be careful with the list boundaries. Pair iteration typically reduces the number of iterations by 1 (since n elements produce n-1 pairs).

  • If the list can have a variable size, ensure you handle cases where it might have 0 or 1 elements. Otherwise, you risk index errors or unexpected behavior.

By following this tutorial, you've learned different techniques to iterate over pairs of consecutive elements in a list in Python. Depending on your needs and your personal coding style, you can choose the method that suits you best.

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