[Numpy-discussion] Comparison of arrays
Francesc Alted
faltet at pytables.org
Mon Feb 9 03:45:02 EST 2009
A Monday 09 February 2009, Nils Wagner escrigué:
> Hi all,
>
> I have two integer arrays of different shape, e.g.
>
> >>> a
>
> array([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
>
> >>> b
>
> array([ 3, 4, 5, 6, 7, 8, 9, 10])
>
> How can I extract the values that belong to the array a
> exclusively i.e. array([1,2]) ?
One possible, fast solution is using Python sets:
In [45]: np.array(list(set(a) ^ set(b)))
Out[45]: array([1, 2])
Although this is suboptimal for very large arrays as it needs temporary
space.
Cheers,
--
Francesc Alted
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