how to sort two dimensional array ??

Stephen Hansen apt.shansen at gmail.com
Tue Jan 19 18:39:53 CET 2010


On Tue, Jan 19, 2010 at 9:00 AM, Robert Somerville <
rsomerville at sjgeophysics.com> wrote:

> Hi;
>

Hi, why did you post this three times?


> i am having trouble trying to sort the rows of a 2 dimensional array by the
> values in the first column .. does anybody know how or have an example of
> how to do this ??? while leaving the remain columns remain relative to the
> leading column
>
> from numpy import *
>
> a=array( [ [4, 4, 3], [4, 5, 2],  [3, 1, 1] ] )
>
> i would like to generate the output (or get the output ...)
>
> b = [ [3,1,1], [4,4,3], [4,5,2] ]
>

I don't use numpy, so this may or may not work. But for a regular python
list-of-lists (2 dimensional array), you simply do:

a.sort(key=lambda x: x[0])

--S
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