[Numpy-discussion] Trying out Numeric3
Chris Barker
Chris.Barker at noaa.gov
Fri Mar 25 09:53:57 EST 2005
Scott Gilbert wrote:
> I don't know what particular meta data you plan to store with the buffer
> itself, and I'm going to resist the urge to guess. You probably have some
> very good use cases. What are you planning?
I don't know what Travis has in mind, but I thought I'd bring up a use
case that I think provides some of the motivation for this.
There are any number of Third arty extensions that could benefit from
being able to directly read the data in Numeric* arrays: PIL, wxPython,
etc. Etc. My personal example is wxPython:
At the moment, you can pass a Numeric or numarray array into wxPython,
and it will be converted to a wxList of wxPoints (for instance), but
that is done by using the generic sequence protocol, and a lot of type
checking. As you can imagine, that is pretty darn slow, compared to just
typecasting the data pointer and looping through it. Robin Dunn, quite
reasonably, doesn't want wxPython to depend on Numeric, so that's what
we've got.
My understanding of this memory object is that an extension like
wxPython wouldn't not need to know about Numeric, but could simply get
the memory Object, and there would be enough meta-data with it to
typecast and loop through the data. I'm a bit skeptical about how this
would work. It seems that the metadata required would be the full set of
stuff in an array Object already:
type
dimensions
strides
This could be made a bit simpler by allowing only contiguous arrays, but
then there would need to be a contiguous flag.
To make use of this, wxPython would have to know a fair bit about
Numeric Arrays anyway, so that it can check to see if the data is
appropriate. I guess the advantage is that while the wxPython code would
have to know about Numeric arrays, it wouldn't have to include Numeric
headers or code.
-Chris
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Christopher Barker, Ph.D.
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