What happens if you enter the command from Geany at a terminal
~/bin/pythonbuild.py
it should run my Python program although it will fail because it does not have a .ino file to work on. If it does not run my Python program then your command is wrong.
Another thought is to enter the command which python
On my PC it gives /usr/bin/python which leads me to think you should not have the tilde at the start of your command.
...R