[Numpy-discussion] PyArray_BASE equivalent in python

[Peter Rennert]

Brilliant thanks, I will try out the "little class" approach.

On 11/26/2013 08:03 PM, Nathaniel Smith wrote:
> On Tue, Nov 26, 2013 at 11:54 AM, Peter Rennert <p.rennert at cs.ucl.ac.uk> wrote:
>> Hi,
>>
>> I as the title says, I am looking for a way to set in python the base of
>> an ndarray to an object.
>>
>> Use case is porting qimage2ndarray to PySide where I want to do
>> something like:
>>
>> In [1]: from PySide import QtGui
>>
>> In [2]: image =
>> QtGui.QImage('/home/peter/code/pyTools/sandbox/images/faceDemo.jpg')
>>
>> In [3]: import numpy as np
>>
>> In [4]: a = np.frombuffer(image.bits())
>>
>> --> I would like to do something like:
>> In [5]: a.base = image
>>
>> --> to avoid situations such as:
>> In [6]: del image
>>
>> In [7]: a
>> Segmentation fault (core dumped)
> This is a bug in PySide -- the buffer object returned by image.bits()
> needs to hold a reference to the original image. Please report a bug
> to them. You will also get a segfault from code that doesn't use numpy
> at all, by doing things like:
>
> bits = image.bits()
> del image
> <anything involving the bits object>
>
> As a workaround, you can write a little class with an
> __array_interface__ attribute that points to the image's contents, and
> then call np.asarray() on this object. The resulting array will have
> your object as its .base, and then your object can hold onto whatever
> references it wants.
>
> -n
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