Problem installing GNU-radio in ubuntu 11.10

Hello, I installed gnuradio in ubuntu 11.10 using the build gnu-radio
But when execute a Python example (such as, I have an

Traceback (most recent call last):
File “./”, line 26, in
from gnuradio import usrp
ImportError: cannot import name usrp

I suppose than I need to reconfigure de path, but I don’t know how.

Please, help