title: How can I use a Python script in the command line without cd-ing to its directory? Is it the PYTHONPATH?
body: <p>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?</p>
  
  <pre><code>$ 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'
  </code></pre>
  
  <p>After cd to the file directory it runs ..</p>
  
  <pre><code>$ python gbmx.py -h
  usage: gbmx.py [-h] [-b]
  </code></pre>
  
  <p>Why can I not make any use of the PYTHONPATH?</p>