[Numpy-discussion] How is NumPy implemented?

Geoffrey Zhu gzhu at peak6.com
Thu Jun 28 17:00:02 EDT 2007

I see. Thanks a lot.  

-----Original Message-----
From: numpy-discussion-bounces at scipy.org
[mailto:numpy-discussion-bounces at scipy.org] On Behalf Of Tom Denniston
Sent: Thursday, June 28, 2007 3:33 PM
To: Discussion of Numerical Python
Subject: Re: [Numpy-discussion] How is NumPy implemented?

That is normal python syntax.  It works with lists.  What is slightly
unusual is the multi-dimensional slicing as in arr[:,10:20].  However,
this is governed by the way python translates bracket[] index calls to
the __getitem__ and __getslice__ methods.  You can try it out yourself
in ipython or your favorite interpretter by writing the following

In [4]: class GetItemInspect(object):
   ...:     def __getitem__(self, slices):
   ...:         print slices

In [5]: GetItemInspect()[:,:,10:]
(slice(None, None, None), slice(None, None, None), slice(10, None,

This allows you to play with the translation semantics.  I'm sure they
are also documented somewhere but I usually find trying many examples


On 6/28/07, Geoffrey Zhu <gzhu at peak6.com> wrote:
> Hi All,
> I am curious how numpy is implemented. Syntax such as x[10::-2] is 
> completely foreign to Python. How does numpy get Python to support it?
> Thanks,
> Geoffrey
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