I thought

import sys
sys.path.append("/home/me/mydir")

is appending a dir to my pythonpath

if I print sys.path my dir is in there.

Then I open a new command and it is not there anymore.

But somehow Python cant import modules I saved in that dir.

What Am I doing wrong?

I read .profile or .bash_profile will do the trick.

Do I have to add:

PATH="/Me//Documents/mydir:$PYTHONPATH"
export PATH

To make it work?

Modifications to sys.path only apply for the life of that Python interpreter. If you want to do it permanently you need to modify the PYTHONPATH environment variable:

PYTHONPATH="/Me/Documents/mydir:$PYTHONPATH"
export PYTHONPATH

Note that PATH is the system path for executables, which is completely separate.

**You can write the above in ~/.bash_profile and the source it using source ~/.bash_profile