Where can i find python module "la" ?

Hi,

I have installed fenics packages for dolfin-1.0.0, with the exception of dolfin itself which is from the trunk (Arch Linux...). Can someone tell me where me and my computer can find la.py?

>>> import dolfin
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/site-packages/dolfin/__init__.py", line 23, in <module>
    import cpp
  File "/usr/lib/python2.7/site-packages/dolfin/cpp/__init__.py", line 40, in <module>
    exec("import %s" % module_name)
  File "<string>", line 1, in <module>
ImportError: No module named la

I realise I need to append a path to PYTHONPATH but don't know what that path should be.
Thanks,
Myles