[Numpy-discussion] Functions for indexing into certain parts of an array (2d)

Robert Kern robert.kern@gmail....
Sat Jun 6 17:39:45 CDT 2009


On Sat, Jun 6, 2009 at 17:34, Alan G Isaac<aisaac@american.edu> wrote:
> On 6/6/2009 6:02 PM Keith Goodman apparently wrote:
>>> def fill_diag(arr, value):
>>     if arr.ndim != 2:
>>         raise ValueError, "Input must be 2-d."
>>     if arr.shape[0] != arr.shape[1]:
>>         raise ValueError, 'Input must be square.'
>>     arr.flat[::arr.shape[1]+1] = value
>
>
> You might want to check for contiguity.
> See diagrv in pyGAUSS.py:
> http://code.google.com/p/econpy/source/browse/trunk/pytrix/pyGAUSS.py

Ah, that's the beauty of .flat; it takes care of that for you. .flat
is not a view onto the memory directly. It is a not-quite-a-view onto
what the memory *would* be if the array were contiguous and the memory
directly reflected the layout as seen by Python.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless
enigma that is made terrible by our own mad attempt to interpret it as
though it had an underlying truth."
  -- Umberto Eco


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