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So, I am trying to sort 2 related lists. One contains Candidate Names, and one contains the Number of Votes the candidates have (candidate in candidate[0] has votes stored in votes[0]).

I found a way to sort votes[] in descending order, whilst keeping the indexes matched. For example if vote[0] becomes vote[3], candidate[0] will also become candidate[3]. I did this using the built-in zip function, but the example I copied from sorted the lists in ascending order, whereas I require them to be sorted in descending order. Here are my lists:

candidates = ['Donald', 'Barack', 'Hillary', 'Mitt']
votes = [9, 7, 1, 3]

And to sort the lists I used:

votes, candidates = (list(t) for t in zip(*sorted(zip(votes, candidates))))

This did exactly what I wanted, except in ascending order, not descending. How do I edit this to sort the lists into Descending order?

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  • Those aren't nested lists, in fact aren't even lists Commented Feb 12, 2019 at 13:38
  • 2
    sorted(zip(votes, candidates), reverse=True) Commented Feb 12, 2019 at 13:40

3 Answers 3

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2

You could just sort the zip of both the list and reverse it

>>> votes = [9, 7, 1, 3]
>>> candidates = ['Donald', 'Barack', 'Hillary', 'Mitt']
>>> 
>>> sorted(zip(votes, candidates), key=lambda x: x[0]) # in ascending order
[(1, 'Hillary'), (3, 'Mitt'), (7, 'Barack'), (9, 'Donald')]
>>>
>>> sorted(zip(votes, candidates), key=lambda x: x[0], reverse=True) # in descending order
[(9, 'Donald'), (7, 'Barack'), (3, 'Mitt'), (1, 'Hillary')]

>>> # and if you want it back in order again;
>>> votes, names = zip(*sorted(zip(votes, candidates), key=lambda x: x[0], reverse=True))
>>> votes
(9, 7, 3, 1)
>>> names
('Donald', 'Barack', 'Mitt', 'Hillary')
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3 Comments

Is there a way to get it to output two lists, like unzipping it?
Sure. But why ? The dataset seems to be closely related ?
Anyway, here you go, votes, names = zip(*sorted(zip(votes, candidates), key=lambda x: x[0], reverse=True))
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using reverse=True:

candidates = ['Donald', 'Barack', 'Hillary', 'Mitt']
votes = [9, 7, 1, 3]

votes, candidates = (list(t) for t in zip(*sorted(zip(votes, candidates))))


print(sorted(votes, reverse=True))
print(sorted(candidates, reverse=True))

OUTPUT:

[9, 7, 3, 1]
['Mitt', 'Hillary', 'Donald', 'Barack']

OR

candidates = ['Donald', 'Barack', 'Hillary', 'Mitt']
votes = [9, 7, 1, 3]

print(sorted(zip(candidates, votes), reverse=True))

OUTPUT:

[('Mitt', 3), ('Hillary', 1), ('Donald', 9), ('Barack', 7)]

EDIT 3:

candidates = ['Donald', 'Barack', 'Hillary', 'Mitt']
votes = [9, 7, 1, 3]

votes, candidates = (list(t) for t in zip(*sorted(zip(votes, candidates), reverse=True)))

print(votes)
print(candidates)

OUTPUT:

[9, 7, 3, 1]
['Donald', 'Barack', 'Mitt', 'Hillary']
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4 Comments

This outputs 2 lists, which is perfect. BUT, the lists are not in sync. Donald should be first, then Barack etc
@DaneBaird why should Donald be first if it is in descending order?
@DaneBaird check Edit 3.
Sorry about that, I realise I didnt specify which list I wanted to sort first! EDIT 3 is perfect
0

Or, slicing for reversing:

candidates = ['Donald', 'Barack', 'Hillary', 'Mitt']
votes = [9, 7, 1, 3]
votes, candidates = (list(t) for t in zip(*sorted(zip(votes, candidates))[::-1]))
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