python extension modules within packages not loading

tyler tyler.retzlaff at gmail.com
Thu Sep 7 02:45:53 CEST 2006


I've written a small python extension but I'm having difficulty loading
it at runtime.  The source for my extension is a module which is a
member of a package is organized as follows.

test/setup.py
test/myutils/__init__.py
test/myutils/netmodule.c

my setup.py file for building / installing looks like this

setup(ext_package = 'myutils',
    ext_modules = [ Extension('net', sources = [ 'myutils/netmodule.c'
]) ],
    packages = [ 'myutils'])

as per the faq I've been building and installing it with

python setup.py build
python setup.py install

which results in the following being installed into my site-packages
directory.

/usr/lib/python2.4/site-packages/myutils/__init__.py
/usr/lib/python2.4/site-packages/myutils/__init__.pyc
/usr/lib/python2.4/site-packages/myutils/net.so

when I run the interpreter and try to import the modules however I get
no joy.

>>>import myutils
>>>import myutils.net
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
ImportError: No module named net

now annoyed I strace the interpreter during the loading of the module
and see.

stat64("myutils", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
stat64("myutils/__init__.py", {st_mode=S_IFREG|0644, st_size=0, ...}) =
0
stat64("myutils/__init__", 0xbf8d3a6c)   = -1 ENOENT (No such file or
directory)
open("myutils/__init__.so", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such
file or directory)
open("myutils/__init__module.so", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No
such file or directory)
open("myutils/__init__.py", O_RDONLY|O_LARGEFILE) = 3

clearly the above corresponds to my first import statement and it
appears to have been successful.  A little further along in the trace
however I see the following.

stat64("myutils", {st_mode=S_IFDIR|0755, st_size=4096, ...}) = 0
stat64("myutils/net", 0xbf8d3ebc)        = -1 ENOENT (No such file or
directory)
open("myutils/net.so", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file
or directory)
open("myutils/netmodule.so", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such
file or directory)
open("myutils/net.py", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file
or directory)
open("myutils/net.pyc", O_RDONLY|O_LARGEFILE) = -1 ENOENT (No such file
or directory)

clearly the above corresponds to my second import statement but for
some reason it fails with ENOENT when trying to open myutils/net.so
which definately exists.

Noticing it appears to be using a relative path I decided to try again
and this time I chdir() to /usr/lib/python2.4/site-extensions directory
before launching the interpreter and it then it works perfectly fine.
Of course I shouldn't have to set my cwd to the site-extensions
directory before using my extension module..

How do I fix this?  What have I done wrong?

Help very much appreciated, thanks.

Tyler




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