Using Geany for development in Linux

noweare:
The ~/bin is where the pythonbuild.py file is, which is home/joe/bin folder

Sorry, I got myself confused. I was thinking of the location of the python interpreter

have you got this line

#!/usr/bin/env python

at the top of your pythonbuild.py file
(It may need to be a different location on your system)

And is the file pythonbuild.py set as executable and do you have execute permission?

Another possibility is to change the command to

python ~/bin/pythonbuild.py

...R