[Numpy-discussion] Is numpy supposed to support the buffer protocol?

Christopher Barker Chris.Barker at noaa.gov
Mon Aug 28 18:25:44 CDT 2006


HI all,

Robin Dunn has been working on adding better support for dumping data 
directly to wxPython from the num* packages. I've been talking to him 
about the new array interface, and he might well support it 
(particularly if one of us contributes code), but in the meantime, he's 
got a number of things working with python buffers. For instance:

wx.Image.SetDataBuffer(dataBuffer)

That sets the data for a wxImage to the buffer handed in. This isn't as 
nice as the array protocol, as it has no way of checking anything other 
than if the length of the buffer is correct, but it is a good way to 
maximize performance for this sort of thing.

he's now working on adding methods for creating wx.Bitmaps directly from 
buffers. In the process if testing some of this, I discovered that 
numarray (which Robin is testing with) works fine, but numpy does not. I 
get:

File "/usr/lib/python2.4/site-packages/wx-2.6-gtk2-unicode/wx/_core.py", 
line 2814, in SetDataBuffer
     return _core_.Image_SetDataBuffer(*args, **kwargs)
TypeError: non-character array cannot be interpreted as character buffer

If I try to pass in a numpy array, while it works great with a numarray 
array.

While I'm a great advocate of the new array protocol, it seems 
supporting the buffer protocol also would be a good idea. I've enclosed 
some simple test code. It works with numarray, but not numpy 1.0b4

Tested with Python 2.4.3, wxPython 2.6.3.0, Linux fedora core4

-Chris





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Christopher Barker, Ph.D.
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Chris.Barker at noaa.gov
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