User guide

NumPy User Guide, Release 1.9.0
from numpy.distutils.misc_util import Configuration
from numpy.distutils.misc_util import get_info
#Necessary for the half-float d-type.
info = get_info(’npymath’)
config = Configuration(’npufunc_directory’,
parent_package,
top_path)
config.add_extension(’npufunc’,
[’multi_type_logit.c’],
extra_info=info)
return config
if __name__ == "__main__":
from numpy.distutils.core import setup
setup(configuration=configuration)
After the above has been installed, it can be imported and used as follows.
>>> import numpy as np
>>> import npufunc
>>> npufunc.logit(0.5)
0.0
>>> a = np.linspace(0,1,5)
>>> npufunc.logit(a)
array([ -inf, -1.09861229, 0. , 1.09861229, inf])
5.3.5 Example Numpy ufunc with multiple arguments/return values
Our final example is a ufunc with multiple arguments. It is a modification of the code for a logit ufunc for data with a
single dtype. We compute (A*B, logit(A*B)).
We only give the C code as the setup.py file is exactly the same as the setup.py file in Example Numpy ufunc for one
dtype, except that the line
config.add_extension(’npufunc’, [’single_type_logit.c’])
is replaced with
config.add_extension(’npufunc’, [’multi_arg_logit.c’])
The C file is given below. The ufunc generated takes two arguments A and B. It returns a tuple whose first element
is A*B and whose second element is logit(A*B). Note that it automatically supports broadcasting, as well as all other
properties of a ufunc.
#include "Python.h"
#include "math.h"
#include "numpy/ndarraytypes.h"
#include "numpy/ufuncobject.h"
#include "numpy/halffloat.h"
/
*
*
multi_arg_logit.c
*
This is the C code for creating your own
*
Numpy ufunc for a multiple argument, multiple
*
return value ufunc. The places where the
5.3. Writing your own ufunc 91