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

David Grant david.grant at telus.net
Mon Nov 1 20:10:35 CST 2004

Bob Ippolito wrote:

> 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.
Well I'll give them a 7/10 just for being pretty.

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