How to Sort a List of Lists by a Specific Index of the Inner Lists?

Sorting Lists of Lists by Inner List Index

Problem:

Given a list of lists, each inner list containing multiple elements, how do we sort the outer list by a specific index of the inner lists?

Example:

Consider the following list of lists:

[[0, 1, 'f'],
[4, 2, 't'],
[9, 4, 'afsd']]

If we want to sort the outer list by the string fields of the inner lists, how would we accomplish this in Python?

Solution:

The solution involves using the operator.itemgetter function. This function allows us to extract a specific element from each inner list and use it as the sorting criterion. Here's how we would use it:

from operator import itemgetter

L = [[0, 1, 'f'], [4, 2, 't'], [9, 4, 'afsd']]
sorted(L, key=itemgetter(2))

Explanation:

• itemgetter(2) returns a function that extracts the third element from each inner list (index 2, starting from 0).
• The key parameter in sorted() specifies the sorting criterion. By using itemgetter(2), we instruct the sort function to use the string field as the sorting key.
• The result is a sorted list of lists, with the order determined by the string fields.

Additional Note:

While itemgetter is an efficient method for sorting by inner list index, for simple cases like this, a lambda function can also be used. However, the lambda function will typically be slower in such cases.

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