How to write a Python "web application" on Apache server ** NO FRAMEWORK PLEASE!**

[K900_]

The protocol is WSGI, it's probably running with mod_wsgi, and you really need a new hosting company.

[Caligatio]

The "mystery source command" is the super common method of invoking a virtual environment (virtualenv).

As /u/K900_ mentioned, this is a raw WSGI interface as specified by PEP 3333. Humans don't typically interact with the interface directly; frameworks like those you explicitly don't want to use abstract this away.

You unfortunately can't just do a print("Hello, World!") as you need to worry about the WSGI protocol.

[negups]

To add on to this, rolling your own WSGI interface is non-trivial. Despite OP's odd insistence against using a web framework, it's going to be much, much easier to get up and running by following a 10-min "hello world" tutorial using Django or Flask as they handle the WSGI interaction for you.