[redland-dev] Redland: Problem With Python-Bindings

[Sean B. Palmer]

Hi Dave et al.,

I've been unable to get Redland's python language bindings to fully
work, despite a significant amount of effort in trying to do so.

The installation of Redland went without a hitch: I installed Raptor
1.3.2 first, and then Redland 0.9.18 using the system Raptor. When I
came to install the 0.9.18.1 bindings, however, I encountered numerous
problems.

At first, there were lots of syntax errors along the lines of:

    /usr/local/share/redland/Redland.i :
      Line 335. Syntax error in input.

Since I'm using Debian Stable, I decided that this was due to an
out-of-date version of SWIG, and grabbed the latest package from the
SWIG site. This stopped the error in make, but the Redland module still
wouldn't import in Python.

I did "$ ldd -d Redland.so", and it came up with some unresolved
dependencies, which looked promising. Googling on this led me to find a
message that you sent earlier this year [1] that advised setting
LD_LIBRARY_PATH, so I did:

    $ export LD_LIBRARY_PATH=/usr/local/lib:/usr/local/BerkeleyDB.4.2/lib

and Redland.so got fully linked this time. I've no idea why it required
me to set LD_LIBRARY_PATH since I'd previously configured Redland using
"--with-bdb=/usr/local/BerkeleyDB.4.2", and ./configure in the bindings
package had detected Redland properly. I'd of course done "make install"
when I built Redland too.

Anyway, unfortunately--and this is the problem that I still can't get
around--I was getting the following kind of error:

    $ python2.3 example.py
    Traceback (most recent call last):
    File "example.py", line 23, in ?
    import RDF
    File "/home/sbp/redland-bindings-0.9.18.1/python/RDF.py",
       line 1851, in ?
    _world=World()
    File "/home/sbp/redland-bindings-0.9.18.1/python/RDF.py",
       line 187, in __init__
    Redland.librdf_python_world_init(self._world)
    AttributeError: 'module' object has no attribute
       'librdf_python_world_init'

Looking at the ldd output again showed the problem:

    $ ldd -d Redland.so
            librdf.so.0 => /usr/local/lib/librdf.so.0 (0x4000f000)
            [...]
    undefined symbol: _Py_NoneStruct        (./Redland.so)
    undefined symbol: PyString_Type (./Redland.so)
    undefined symbol: PyExc_TypeError       (./Redland.so)
    undefined symbol: PyTuple_Type  (./Redland.so)
    undefined symbol: PyInt_Type    (./Redland.so)
    undefined symbol: PyList_Type   (./Redland.so)
    undefined symbol: PyInstance_Type       (./Redland.so)
    undefined symbol: PyType_Type   (./Redland.so)
    undefined symbol: PyExc_NameError       (./Redland.so)

I did quite a bit of Googling on the "undefined symbol" errors, and
decided that this was due to Python not having been built using
--enable-shared. I downloaded Python 2.4 and rebuilt Redland and the
bindings, and this resolved some of the symbols to the point where
example.py managed to run half way through, and then was unable to
resolve q.run_as_bindings.

Looking at ldd again, only the following symbols were undefined this
time: _Py_NoneStruct, PyString_Type, PyExc_TypeError, PyInt_Type,
PyType_Type, PyExc_NameError. I decided that since I'm using Debian
Stable, perhaps something wasn't up-to-date enough for Redland and it
wasn't detecting it (a la the SWIG problem mentioned earlier).

Using testing/unstable pacakges on stable isn't really an option, so I
decided to reinstall Debian from scratch on a new filesystem and use
Debian unstable (Sid). It took a few hours, but then I was able to use
"aptitude install rdflib0" to install redland, and get the Python
bindings too. Note that the advice in [2] is out-of-date now: the
packages for Redland are in Debian Unstable, so you *don't* need to add
the lines to /etc/apt/sources.list as it says.

Need I say how the python bindings installation went?

    $ python2.3
    Python 2.3.4 (#2, Aug  5 2004, 09:33:45)
    [GCC 3.3.4 (Debian 1:3.3.4-7)] on linux2
    Type "help", "copyright", "credits" or "license" for more
    information.
    >>> import RDF
    Traceback (most recent call last):
      File "<stdin>", line 1, in ?
      File "/usr/lib/python2.3/site-packages/RDF.py", line 118, in ?
        import Redland
    ImportError: /usr/lib/python2.3/site-packages/Redland.so: undefined
    symbol: librdf_error
    >>>

I also tried building the redland bindings package straight again, but
this time it fails to even find the system version of Redland that I
installed using aptitude (the replacement for apt-get).

So that's my installation saga! The closest I managed to come was by
using Python2.4-alpha on Debian Stable, but even then it wasn't really
working. I'd very much like to be able to do some Python development
using Redland, so I'm really hoping that I've given you enough
information here to be able to resolve this. I know it's frustrating
when someone lodges a five page bug report--especially when there's
probably a two line solution--but as you can see, this wasn't a quick
five-minutes-and-give-up sort of situation.

Cheers,

[1] [redland-dev] Problems with Tcl interface...
http://lists.usefulinc.com/pipermail/redland-dev/2004-March/000451.html
[2] http://www.redland.opensource.ac.uk/dist/binaries/debian/README

-- 
Sean B. Palmer, http://inamidst.com/