Problematic error embedding Python using boost::python

Hello all,

First of all i'd like to say that i don't know much if anything at all about
the inner workings of boost::python; however, i am familar with the Python C
API. The following problem persists at the moment, leaving me/us (developers
on the project) partially stuck.

Our application acts a a scripting host for scripts which access parts of
the application's C++ API, exposed via boost::python. Using a typical
loading procedure, our app loads scripts, which define a particular class
derived from a base class we provide, which the C++ host instantiates in
C/C++-space (the scripts only provide the class, do not execute any code
beyonc the scope of the class).

Whenever the application starts up, we randomly (sometimes not at all)
receive an error like this:

  if state == mpx.PlayStatus.STOPPED:
Traceback (most recent call last):
  File "/usr/share/mpx/scripts/trackinfo/__init__.py", line 498, in
pstate_changed
    if state == mpx.PlayStatus.STOPPED:
TypeError: expected string or Unicode object, NoneType found

However, 'mpx' itself a module, 'state' is variable which positively has a
value assigned to it, and 'PlayStatus', 'STOPPED' are defined in C++ using
boost python. It seems it it is not an error with the python code itself, as
it spuriously appears (only once for the entire session of the application)
at various points of execution/with various scripts.

Tracing it back to C++-space didn't come up with any results yet so far
either.

Is this a problem in how boost::python wraps classes into Python? So far
we're really sure this isn't a problem with our code, but we're not sure
where to look further (trying with the plain C API would be immensely
tedious at this moment, boost::python is a real timesaver!)

Does anyone know about this issue, or has seen similar?

TIA

Milosz Derezynski

PS:

The code defining these classes can be found here:
http://hg.backtrace.info/hgwebdir.cgi/mpx/file/cf1967218a68/mpx/mpx-py.cc

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