How to Sort Lists or Tuples of Lists/Tuples by a Specific Index Element?

Sorting Lists/Tuples of Lists/Tuples by Element at a Specific Index

Sorting lists or tuples of lists or tuples based on an element at a specific index can be achieved using lambda functions. The common approach is to use the built-in sorted() function or the list/tuple's sort() method with a custom key function.

For instance, considering the given data:

data = [[1,2,3], [4,5,6], [7,8,9]]
data = [(1,2,3), (4,5,6), (7,8,9)]

To sort by the second element of each subset, you can use the following snippet:

sorted_by_second = sorted(data, key=lambda tup: tup[1])

Alternatively, you can sort in place using the sort() method:

data.sort(key=lambda tup: tup[1])

By default, sorting is done in ascending order. To sort in descending order, specify reverse=True:

sorted_by_second = sorted(data, key=lambda tup: tup[1], reverse=True)
data.sort(key=lambda tup: tup[1], reverse=True)

Note that using tuples instead of lists preserves immutability, which may be desired in some scenarios.

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