python extensions: including project local headers
J Kenneth King
james at agentultra.com
Fri Oct 24 17:11:44 CEST 2008
Philip Semanchuk <philip at semanchuk.com> writes:
> On Oct 23, 2008, at 3:18 PM, J Kenneth King wrote:
>> Philip Semanchuk <philip at semanchuk.com> writes:
>>> On Oct 23, 2008, at 11:36 AM, J Kenneth King wrote:
>>>> Hey everyone,
>>>> I'm working on a python extension wrapper around Rob Hess'
>>>> implementation of a SIFT feature detector. I'm working on a
>>>> computer-vision based project that requires interfacing with
>>>> Python at
>>>> the higher layers, so I figured the best way to handle this would be
>>>> C (since my initial implementation in python was ungodly and slow).
>>>> I can get distutils to compile the extension and install it in the
>>>> python path, but when I go to import it I get the wonderful
>>>> ImportError: /usr/lib/python2.5/site-packages/pysift.so: undefined
>>>> symbol: _sift_features
>>> You're close but not interpreting the error quite correctly. This
>>> isn't an error from the compiler or preprocessor, it's a library
>>> error. Assuming this is dynamically linked, your OS is reporting
>>> at runtime, it can't find the library that contains _sift_features.
>>> Make sure that it's somewhere where your OS can find it.
>> This is basically what I was looking for help with. So far the project
>> directory is:
>> I thought I could just #include "sift.h" in pysift.c as long as
>> distutils passed the right -I path to gcc.
> That's true, and it sounds like you've got that part working.
>> Maybe I should compile the sift code as a shared object and link it to
>> my extension? How would I get distutils to build the makefile and tell
>> gcc how to link it?
>> Thanks for the reply. Python has spoiled me and my C is rather
>> rusty. :)
> I don't know how to get setup.py to build a shared object separately.
> I am in the same Python/C situation as you. I'm scrubbing the rust off
> of my C skills and I'm also a n00b at developing extensions. I've
> learned a lot from looking at other people's setup code, so maybe I
> can help you there.
> My posix_ipc module links to the realtime lib "rt" and here's the
> relevant snippets of setup.py:
> import distutils.core as duc
> libraries = [ ]
> source_files = ["posix_ipc_module.c"]
> ext_modules = [ duc.Extension("posix_ipc",
> duc.setup(name="posix_ipc", version=VERSION, ext_modules=ext_modules)
> You can download the whole thing here if you want to examine all the
I'll take a look, thanks! :)
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