I'm guessing you could use Cython to make this easier. It's usually used for calling C from Python, but can do the sandwich in both directions... Just a thought -- it will help with some of that boilerplate code... -CHB On Tue, Jan 30, 2018 at 10:57 PM, Jialin Liu wrote:

Amazing! It works! Thank you Robert.

I've been stuck with this many days.

Best, Jialin LBNL/NERSC

On Tue, Jan 30, 2018 at 10:52 PM, Robert Kern wrote:

...

On Wed, Jan 31, 2018 at 3:25 PM, Jialin Liu wrote:

...

Hello, I'm extending C with python (which is opposite way of what people usually do, extending python with C), I'm currently stuck in passing a C array to python layer, could anyone plz advise?

I have a C buffer in my C code and want to pass it to a python function. In the C code, I have:

npy_intp dims [2];

...

dims[0] = 10; dims[1] = 20; import_array(); npy_intp m=2; PyObject * py_dims = PyArray_SimpleNewFromData(1, &m, NPY_INT16 ,(void *)dims ); // I also tried NPY_INT PyObject_CallMethod(pInstance, method_name, "O", py_dims);

In the Python code, I want to just print that array:

def f(self, dims):

print ("np array:%d,%d"%(dims[0],dims[1]))

But it only prints the first number correctly, i.e., dims[0]. The second number is always 0.

The correct typecode would be NPY_INTP.

-- Robert Kern

_______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@python.org https://mail.python.org/mailman/listinfo/numpy-discussion

_______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@python.org https://mail.python.org/mailman/listinfo/numpy-discussion

-- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker@noaa.gov

You can also check out pybind11, xtensor, and xtensor-python The latter enables a high-level numpy-like API on the C++ side. You can check out the numpy to xtensor cheat sheet: http://xtensor.readthedocs.io/en/latest/numpy.html Best, Sylvain On Thu, Feb 1, 2018 at 12:11 AM, Stefan Seefeld wrote:

On 31.01.2018 17:58, Chris Barker wrote:

I'm guessing you could use Cython to make this easier.

... or Boost.Python (http://boostorg.github.io/python), which has built-in support for NumPy (http://boostorg.github.io/ python/doc/html/numpy/index.html), and supports both directions: extending Python with C++, as well as embedding Python into C++ applications.

[image: Stefan]

--

...ich hab' noch einen Koffer in Berlin...

_______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@python.org https://mail.python.org/mailman/listinfo/numpy-discussion

With PyObject_CallMethod(pInstance, method_name, "O", py_dims); Can I pass in a reference and modify its content in python? Best, Jialin On Sat, Feb 3, 2018 at 10:29 AM, Jialin Liu wrote:

Thank you guys.

Best, Jialin

Sent from my iPhone

On Feb 3, 2018, at 8:11 AM, Sylvain Corlay wrote:

You can also check out pybind11, xtensor, and xtensor-python

The latter enables a high-level numpy-like API on the C++ side.

You can check out the numpy to xtensor cheat sheet:

http://xtensor.readthedocs.io/en/latest/numpy.html

Best,

Sylvain

On Thu, Feb 1, 2018 at 12:11 AM, Stefan Seefeld wrote:

...

On 31.01.2018 17:58, Chris Barker wrote:

I'm guessing you could use Cython to make this easier.

... or Boost.Python (http://boostorg.github.io/python), which has built-in support for NumPy (http://boostorg.github.io/pyt hon/doc/html/numpy/index.html), and supports both directions: extending Python with C++, as well as embedding Python into C++ applications.

--

...ich hab' noch einen Koffer in Berlin...

_______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@python.org https://mail.python.org/mailman/listinfo/numpy-discussion

_______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@python.org https://mail.python.org/mailman/listinfo/numpy-discussion