1) I was wondering how much shell experience the intended audience has at this point. Would they understand this step? 
2) would this be better in case PYTHONPATH is set:

echo 'export PYTHONPATH=/usr/local/share/khmer/python:$PYTHONPATH' >> ~/.bashrc

3) When they get back and try to redo this stuff at home, would this make the operation more universal (but less explicit):
cd python
echo 'export PYTHONPATH=$PWD:$PYTHONPATH' >> ~/.bashrc