Question

Coming from MATLAB, I am looking for some way to create functions in Python which are derived from wrapping C functions. I came across Cython, ctypes, SWIG. My intent is not to improve speed by any factor (it would certainly help though).

Could someone recommend a decent solution for such a purpose.
Edit: What’s the most popular/adopted way of doing this job?

Thanks.

Answer 1

I’ve found that weave works pretty well for shorter functions and has a very simple interface.

To give you an idea of just how easy the interface is, here’s an example (taken from the PerformancePython website). Notice how multi-dimensional array conversion is handled for you by the converter (in this case Blitz).

from scipy.weave import converters

def inlineTimeStep(self, dt=0.0):
    """Takes a time step using inlined C code -- this version uses
    blitz arrays."""
    g = self.grid
    nx, ny = g.u.shape
    dx2, dy2 = g.dx**2, g.dy**2
    dnr_inv = 0.5/(dx2 + dy2)
    u = g.u

    code = """
           #line 120 "laplace.py" (This is only useful for debugging)
           double tmp, err, diff;
           err = 0.0;
           for (int i=1; i<nx-1; ++i) {
               for (int j=1; j<ny-1; ++j) {
                   tmp = u(i,j);
                   u(i,j) = ((u(i-1,j) + u(i+1,j))*dy2 +
                             (u(i,j-1) + u(i,j+1))*dx2)*dnr_inv;
                   diff = u(i,j) - tmp;
                   err += diff*diff;
               }
           }
           return_val = sqrt(err);
           """
    # compiler keyword only needed on windows with MSVC installed
    err = weave.inline(code,
                       ['u', 'dx2', 'dy2', 'dnr_inv', 'nx', 'ny'],
                       type_converters=converters.blitz,
                       compiler = 'gcc')
    return err