# [Numpy-discussion] Efficient removal of duplicates

Hanno Klemm klemm@phys.ethz...
Tue Dec 16 03:09:33 CST 2008

```Thanks Daran,

that works like a charm!

Hanno

On Tue, Dec 16, 2008, Daran Rife <drife@ucar.edu> said:

> Whoops! A hasty cut-and-paste from my IDLE session.
>
> import numpy as np
>
> a = [(x0,y0), (x1,y1), ...] # A numpy array, but could be a list
> l = a.tolist()
> l.sort()
> unique = [x for i, x in enumerate(l) if not i or x != l[i-1]] # <----
> a_unique = np.asarray(unique)
>
>
> Daran
>
> --
>
> On Dec 15, 2008, at 5:24 PM, Daran Rife wrote:
>
>> How about a solution inspired by recipe 18.1 in the Python Cookbook,
>> 2nd Ed:
>>
>> import numpy as np
>>
>> a = [(x0,y0), (x1,y1), ...]
>> l = a.tolist()
>> l.sort()
>> unique = [x for i, x in enumerate(l) if not i or x != b[l-1]]
>> a_unique = np.asarray(unique)
>>
>> Performance of this approach should be highly scalable.
>>
>> Daran
>>
>> --
>>
>>
>> Hi,
>>
>> I the following problem: I have a relatively long array of points
>> [(x0,y0), (x1,y1), ...]. Apparently, I have some duplicate entries,
>> which
>> prevents the Delaunay triangulation algorithm from completing its
>>
>> Question, is there an efficent way, of getting rid of the duplicate
>> entries?
>> All I can think of involves loops.
>>
>> Thanks and regards,
>> Hanno
>
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>

--
Hanno Klemm
klemm@phys.ethz.ch

```