Am Donnerstag, 7. März 2013 schrieb Cyril Roelandt:
>  From setup.py:
> # those are examined to find
> # - libxml2/libxml/tree.h
> # - iconv.h
> # - libxslt/xsltconfig.h
> includes_dir = [
> "/usr/include",
> "/usr/local/include",
> "/opt/include",
> os.path.join(ROOT,'include'),
> HOME
> ];
> 
> You could patch setup.py to add the right path. Or you could run
> "configure" in libxml2 with "--prefix=<yourprefix>", then cd into the
> "python" directory, and ROOT will be set to <youprefix> in setup.py.

Thanks for your help! Indeed, when running "setup.py install" from the guix 
builder, libxml2 is found after installing it, so the "--prefix" is 
honoured. However, then iconv.h is searched for in the given list of paths, 
which does not include /nix/store/...glibc.../include, and the CPATH is not 
taken into account, so iconv.h is not found.

I tried adding glibc as an explicit input and to overwrite the path in 
setup.py. However, that does not use the glibc of the CPATH, but builds 
another one on top of it. Do I understand it correctly that I need to use 
glibc-final instead?

> Try:
> $ python setup.py install --prefix=/path/to/foo/bar
> You may have to adjust $PYTHONPATH to something like:
> /path/to/foo/bar:$PYTHONPATH
> for this to work.

Specifying no --prefix, it now tries to install a file as
   /nix/store/j8f28wavspyic8g9didl1ninaz48vdq0-
python-2.7.3/lib/python2.7/site-packages/libxml2mod.so
which fails since this is another package, not libxml2.
Giving as --prefix the output path, files are instead installed into
   /nix/store/svnw8fq87qrfrpcs7grx5nram558ahkp-
libxml2-2.9.0/lib/python2.7/site-packages/
which looks reasonable.

I am attaching the resulting patch. Is it reasonable to apply it to the 
libxml2 package, or would it be preferable to create a separate libxml2-
python package?

Andreas