[Discuss-gnuradio] ImportError: cannot import name usrp

[teka yemane]

I have installed gnuradio3.1.3 and executed the 'export PYTHONPATH=/usr/local/lib/python2.5/site-packages' command. Then,
the command 'from gnuradio import usrp' doesn't result in an error when executed from the gnuradio folder
but when I cd to my custom demodulator block which is also located on the gnuradio folder, and execute my python file, it outputs
the following error:
address@hidden python]# ./usrp_fsk4_oscope.py
Traceback (most recent call last):
  File "./usrp_fsk4_oscope.py", line 26, in <module>
    from gnuradio import usrp
ImportError: cannot import name usrp

I have tried several times but it still gives out the same error. I have also installed all the dependencies for the gnuradio
for fedora and used './configure --enable-all-components' option when I install the gnuradio. I don't have the USRP hardware now
but I want to take input from local files instead of the usrp.
Any suggestions please!
Thanks,
teka