In the Biopython installation instructions, it says that if Biopython doesn\'t work I\'m supposed to do this:
export PYTHONPATH = $PYTHONPATH\':/directory/where/you/
You can add the directory to your sys.path list
import sys
biopythondir = '/where/you/put/biopython'
if biopythondir not in sys.path:
sys.path.append(biopythondir)
# import seq
Or, for a more elegant solution than mucking around with environment variables and sys.path, see how to use .pth files to extend sys.path.