PythonPath file

[JohnRLaw]

I am a beginning python programmer. My computer is running Linux Mint 17.3. I am using IDLE as the development environment. My question is simple. I know how to set a Pythonpath temporarily for a session. I want to include one or two directories in the path permanently. I also understand I can do that by appending the directories to the path file because it is a list. My problem is that I cannot find the file and I have searched with a number of extensions. If someone can tell me where I should start to look I would be very grateful.

Thanks.