Trier par index 2D Array Python

a = [[9, 9, 2], [9, 9, 3], [9, 9, 8], [9, 9, 4], [9, 9, 1], [9, 9, 5]]

b = sorted(a, key=lambda a:a[2])

#b contains the following arrays, sorted by their second index:
[[9, 9, 1], [9, 9, 2], [9, 9, 3], [9, 9, 4], [9, 9, 5], [9, 9, 8]]
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