multidimensional arrays from python to C

[Fernando Pérez]

Chris Fonnesbeck wrote:

> I am embedding some python code in C, and need to be able to take a
> multidim. array from python and assign its values to a global double
> array in C.  Can this python array simply be cast into a C double
> type, and assigned to the array in question, or do I have to do a
> multiple-nested loop to assign each element individually.  Hope this
> makes sense!

You should take a look at weave (scipy.org). It allows you to write things 
like:

#-----------------------------------------------------------------------------
# Returning a scalar quantity computed from a Numeric array.
def trace(mat):
    """Return the trace of a matrix.
    """
    nrow,ncol = mat.shape
    # The following is embedded C code:
    code = \
"""
double tr=0.0;
for(int i=0;i<nrow;++i)
    tr += mat(i,i);
return_val = Py::new_reference_to(Py::Float(tr));
"""
    return weave.inline(code,['mat','nrow','ncol'],
                        type_converters = converters.blitz)


If you look at http://www-hep.colorado.edu/~fperez/python/python-c/ you'll 
find some examples of basic weave usage which should get you started in 10 
minutes.

Cheers,

f.