exposing C array to python namespace: NumPy and array module.

Bo Peng bpeng at rice.edu
Sat Jan 1 01:18:52 CET 2005


Dear list,

I am writing a Python extension module that needs a way to expose pieces 
of a big C array to python. Currently, I am using NumPy like the following:

  PyObject* res = PyArray_FromDimsAndData(1, int*dim, PyArray_DOUBLE, 
char*buf);

Users will get a Numeric Array object and can change its values (and 
actually change the underlying C array).

This works fine. However, when I deliver my module, I find NumPy is 
unnecessarily large for this simple task. As a matter of fact, I had to 
  build from source NumPy, ATLAS etc on Solaris, Linux, Mac.... and if a 
user would like to use my module, he has to do the same thing!

Python's array module is built-in, easy to use, but *without* a 
FromLenAndData function! Even the buffer interface provides only 'get 
buffer' but no 'set buffer' functions. Could anyone tell me how I can 
create an array object from existing data? Some vague ideas might be 
used: 1. PyCObject (I do not really understand the manual), 2. copy and 
modify arraymodule.c to my project (doable at all? License issue?) 3. 
Create an array object and hack it. (no api to do this.)

I would strongly suggest an arraymodule.h with Array_FromLenAndData.

Many thanks in advance.
Bo



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