Brian Blais wrote:
> Hello,
>
> I have two lists, one with strings (filenames, actually), and one with a
> real-number
> rank, like:
>
> A=['hello','there','this','that']
> B=[3,4,2,5]
>
> I'd like to sort list A using the values from B, so the result would be
> in this example,
>
> A=['this','hello','there','that']
Here are two ways:
>>> A=['hello','there','this','that']
>>> B=[3,4,2,5]
>>> zip(*sorted(zip(B,A)))[1]
('this', 'hello', 'there', 'that')
>>> [a for b,a in sorted(zip(B,A))]
['this', 'hello', 'there', 'that']
I prefer the second one, I think it is more readable, will use less
memory (doesn't have to create a new list B in the final step) and it's
even faster on my computer:
D:\Projects\CB>python -m timeit -s
"A=['hello','there','this','that'];B=[3,4,2,5]" "zip(*sorted(zip(B,A)))[1]"
100000 loops, best of 3: 6.29 usec per loop
D:\Projects\CB>python -m timeit -s
"A=['hello','there','this','that'];B=[3,4,2,5]" "[a for b,a in
sorted(zip(B,A))]"
100000 loops, best of 3: 5.53 usec per loop
(I'm bored this morning :-)
There's probably a clever way to do it using the key parameter to sort
but I can't think of it...
>
> The sort method on lists does in-place sorting. Is there a way to do
> what I want here?
The example above does not sort in place, if you want it to be in place use
A[:] = [a for b,a in sorted(zip(B,A))]
Kent
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