Re: [Boost-users] Numpy ndarray as argument or return value using boost python

Subject: Re: [Boost-users] Numpy ndarray as argument or return value using boost python
From: OvermindDL1 (overminddl1_at_[hidden])
Date: 2009-11-30 20:02:46

On Mon, Nov 30, 2009 at 1:34 PM, Nyiro Gergo <gergo.nyiro_at_[hidden]> wrote:
> - Hide quoted text -
> - Show quoted text -
> <http://groups.google.com/group/boost-list/browse_thread/thread/b491f5eb8cc836c5?hide_quotes=no#msg_a69011d99e445aef>
>
> On Mon, Oct 12, 2009 at 7:09 AM, Pim Schellart <p.schell...
> <http://groups.google.com/groups/unlock?_done=/group/boost-list/browse_thread/thread/b491f5eb8cc836c5&msg=a69011d99e445aef>@gmail.com>
> wrote:
>>> Hi Everyone,
>
>>> I tried to find a good example for this but after spending two days on
>>> google and one day getting pyublas to compile I decided to call for
>>> help.
>>> I want to give a numpy ndarray as an argument to a c++ method,
>>> calculate something and return the output as an ndarray to Python.
>>> I would prefer not to use another library (such as PyUblas) for this
>>> so I do not have to add another dependency to my program.
>>> Since the latest information on boost python is quite outdated (uses
>>> numeric) I would like to know the following.
>
>>> 1. Is boost python still maintained or should I switch to another tool.
>>> 2. Is numpy supported, and if so,
>>> 3. can someone give me a basic example of how to use it.
>
>> 1. Yes, Boost.Python is still maintained and works find.
>> 2. Yes, Boost.Python supports any and all libraries that communicate
>> through python, you would just use the ndarray just like any other
>> Python Object.
>> 3. Give an example of how you use it in Python and we can give you an
>> example of how you would do it from the C++ side, it is a pretty
>> direct 1-to-1 mapping (have you gone through the Boost.Python
>> tutorials and documentation yet?).
>
> Hello,
>
> I read that post above on Boost-users mailing list, but I have no permission
> required to post. To answer to the 3. point could you give me an example how
> to solve this python code snippet in C++:
>>>> parser = cParser('FileName') # that would be the C++ class (already
>>>> implemented)
>>>> TimeAndSignal = parser.getSignal('SignalName') # and this the
>>>> questionable member function
>>>> type(TimeAndSignal)
> <type, 'list'>
>>>> len(TimeAndSignal)
> 2
>>>> type(TimeAndSignal[0])
> <type, 'ndarray'>
>>>> type(TimeAndSignal[1])
> <type, 'ndarray'>
>>>> import pylab
>>>> pylab.plot(TimeAndSignal[0], TimeAndSignal[1]); pylab.show()
>>>> Time, Signal = parser.getSignal('SignalName') # and this must work too
>>>> pylab.plot(Time, Signal); pylab.show()
>
> Thanks for your help in advance.

You should forward this to the Boost list.  I am not home right now so
cannot give a good example, so you would probably get a much better
example from there.  I am forwarding this response back to the Boost
list.  If I notice this later when I have free time, I will come up
with examples for the above, but it really is very simple, should look
at the examples included with Boost.Python.