[SciPy-user] FYI: C++ Extensions for Python

Bob Ippolito bob at redivi.com
Mon Nov 1 19:59:41 CST 2004


On Nov 1, 2004, at 19:03, David Grant wrote:

> Bob Ippolito wrote:
>
>>
>> On Nov 1, 2004, at 17:51, David Grant wrote:
>>
>>> Just thought I'd share my experiences concerning looking for a way 
>>> to make python interfaces for C++ code (see my previous thread about 
>>> this):
>>>
>>> pycxx - Looks like it requires one to modify all the C++ source, 
>>> adding PyObject pointers everywhere.  I stayed away from this.  I 
>>> don't want to modify the code if I have to (why should I have to?  
>>> the reason I'm making an interface is so that I can use the C++ 
>>> code, and not touch it, thus avoiding creating bugs in the C++ code. 
>>>  If I WANTED to touch the C++ code I'd just re-write in python).
>>>
>>> boost.python - Horrible documentation and horrible setup.  Nothing 
>>> good to say about this.  I spent more time on this than any other 
>>> method and made the least progress.
>>>
>>> weave - was going to write a python routine which had some small 
>>> piece weave code.  The weave code would be talking to a C++ library 
>>> or compiled python extension or something.  I was able to make a C++ 
>>> library containing all my C++ code but then abandoned it after that, 
>>> to see if there were simpler methods
>>>
>>> python.org method - http://docs.python.org/ext/simpleExample.html - 
>>> Similar to pycxx it involved altering the code
>>>
>>> swig - at first it seemed like a lot of work to copy everything from 
>>> the .h files into the .i file.  But then I realized you can just use 
>>> %include and it will use that stuff for swig.  Simple examples are 
>>> given in the docs for both C and C++ which work well.  I like how it 
>>> just generates an extra .c wrapper file which is then compiled to a 
>>> .o file and linked together will all the other .o files and 
>>> libraries (like -llapack) into a python extension, very simply.  
>>> Extend any methods or functions you want.  I had a problem because 
>>> the C++ class overloaded the operator+ method, but there is any easy 
>>> to fix that in the docs, calling the python wrapper __add__ instead.
>>>
>>> So far swig is my choice.  Boost.python looked good but I simple 
>>> couldn't get bjam to work!
>>
>>
>> Uh, where does it say that you need to use bjam?  It works just fine 
>> outside of that environment...  take a look at Fusion 
>> <http://itamarst.org/software/> for example.
>>
> This page calls itself a quickstart but it doesn't say how to build 
> the shared library or what to do with the "Boost.Python" wrapper:
> http://www.boost.org/libs/python/doc/tutorial/doc/quickstart.html
>
> The next page in the tutorial which is very Windows specific (I don't 
> use Windows) and doesn't get me from A to B.  ie. it should get a 
> hello.cpp python module but it doesn't.  It seems to want me to run 
> boost in an example directory which is under /usr/share.  Not the 
> right place to be building anything!
>
> This page also doesn't talk about making the wrapper and/or what to 
> name it, or what to do with it. It only talks about bjam

Ok, fine, so the tutorials and quickstart aren't the greatest.  No real 
surprise there.  Take a look at Fusion's setup.py.

-bob



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