Sort list of list in python

Question

I have this list structure:

[[[6], [4], 1.0], [[5, 6], [4], 1.0], [[5], [6], 1.0], [[5], [4, 6], 1.0], [[5], [4], 1.0], [[4, 5], [6], 1.0], [[4], [6], 0.8]]

And I want to sort it via the 3rd element (descending order) and the lengths of the first and second list (first the ones which are smaller). I tried using

r = sorted(r, key=itemgetter(2, 0, 1), reverse=True)

which sorts the 3rd element in descending order, but how can I add the other sorting restrictions to this one?

Expected output:

[[[6], [4], 1.0], [[5], [6], 1.0], [[5], [6], 1.0], [[5], [4], 1.0], [[5], [4, 6], 1.0], [[5, 6], [4], 1.0], [[4, 5], [6], 1.0], [[4], [6], 0.8]]

@DeepSpace I edited the question to show you the expected output. But basically as I said, I want it to be sorted first given the 3rd element, and then for the length of the first and second list (shortest first) — Fjallbacka
– Fjallbacka, Commented Nov 2, 2017 at 13:26
@JHBonarius no its not a duplicate, I need 2 sorting restrictions in this case.. — Fjallbacka
– Fjallbacka, Commented Nov 2, 2017 at 13:28

yinnonsanders · Accepted Answer · 2017-11-02 13:58:32Z

2

Use a lambda expression:

r = sorted(r, key=lambda x:(x[2], -len(x[0]), -len(x[1])), reverse=True)

or sort without reassignment:

r.sort(key=lambda x:(x[2], -len(x[0]), -len(x[1])), reverse=True)

edited Nov 2, 2017 at 13:58

answered Nov 2, 2017 at 13:37

yinnonsanders

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1 Comment

JHBonarius Over a year ago

Almost right. you need to inverse the size, because he wants the smallest first r.sort(key=lambda x:(x[2], -len(x[0]), -len(x[1])), reverse=True)

Charlie Allatson · Accepted Answer · 2017-11-02 13:48:29Z

I don't believe you could do this in one line, you would need to do in stages like this, with the primary key last:

a = [[[6], [4], 1.0], [[5, 6], [4], 1.0], [[5], [6], 1.0], [[5], [4, 6], 1.0],
     [[5], [4], 1.0], [[4, 5], [6], 1.0], [[4], [6], 0.8]]
b = sorted(a, key=lambda x : len(x[1]), reverse=False)
c = sorted(b, key=lambda x : len(x[0]), reverse=False)
d = sorted(c, key=itemgetter(2), reverse=True)

This gives the correct result:

>>> d [[[6], [4], 1.0], [[5], [6], 1.0], [[5], [6], 1.0], [[5], [4], 1.0], [[5], [4, 6], 1.0], [[5, 6], [4], 1.0], [[4, 5], [6], 1.0], [[4], [6], 0.8]]

See the docs for more information.

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