Need help using PYTHONPATH

Question

How can I make any use of PYTHONPATH? When I try to run a script in the path the file is not found. When I cd to the directory holding the script the script runs. So what good is the PYTHONPATH?

$ echo $PYTHONPATH
:/home/randy/lib/python

$ tree -L 1 '/home/randy/lib/python' 
/home/randy/lib/python
├── gbmx_html.py
├── gbmx.py
├── __init__.py
├── __pycache__
├── scripts
└── yesno.py

$ python gbmx.py -h
python: can't open file 'gbmx.py': [Errno 2] No such file or directory

$ cd '/home/randy/lib/python'

After cd to the file directory it runs ..

$ python gbmx.py -h
usage: gbmx.py [-h] [-b]

Why can I not make any use of the PYTHONPATH?

Answer 1

You're confusing PATH and PYTHONPATH. You need to do this:

export PATH=$PATH:/home/randy/lib/python 

PYTHONPATH is used by the python interpreter to determine which modules to load.

PATH is used by the shell to determine which executables to run.

Answer 2

PYTHONPATH only affects import statements, not the top-level Python interpreter's lookup of python files given as arguments. More on...Path settings in Python

Comments

Hey @iangregor! Can you please tell me if it is possible to change the PYTHONPATH? If yes, then how?

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Try appending to PYTHONPATH instead of overwriting it completely.

export PYTHONPATH=$PYTHONPATH:/home/dev/python-files