sinc_interp.py

def sinc_interp(x, s, u):
    """
    Interpolates x, sampled at "s" instants
    Output y is sampled at "u" instants ("u" for "upsampled")
            
    """
    
    if len(x) != len(s):
        raise Exception, 'x and s must be the same length'
    
    # Find the period    
    T = s[1] - s[0]    
    
    transposed = np.transpose(np.tile(np.arange(len(s)), (len(u),1))) * T    
    
    sincM = np.tile(u, (len(s), 1)) - transposed
    y = np.dot(x, np.sinc(sincM / T))
    
    return y

That's a quick python implementation for the Whittaker–Shannon interpolation