[PD] launching pd from python

[altern]

hi

I have a program in python that does graphics and talks to PD via OSC. 
Up to now i have run manually both the python app and the PD file. BUt 
now I am trying to launch PD from the python code but i cannot make it work.

My understanding is that i should use some command from python os module 
such as spawnl() so that it opens the process of launching without 
bocking the python graphics.

The system is OSX 10.3.9 and PD is copied next to the main python file 
that i am running.
I am doing some basic tests now that that look more or less like this.

#
execdir = os.path.dirname(sys.argv[0])
pdexc = os.path.join(execdir, 
"/Pd-0.38-4-extended-RC1.app/Contents/MacOS/Pd")
arg = os.path.join(execdir, "audio.pd")
os.spawnl(os.P_NOWAIT, pdexc, arg)
# etc ...

Any tips about this? i dont understand why this is not doing its work. 
Probably I am missing some important detail...

thanks

-- 
altern