Put all code that we reuse across weeks in an importable library

[dniku]

Currently, our directory structure is basically a bunch of week* folders at the top level. However, some code is consistently reused across weeks, the most prominent example being launching xvfb. I propose to put all reusable code into a top-level directory called practical_rl.

In this case, all notebooks will have to start with

import sys
sys.path.append('..')

import practical_rl
practical_rl.create_display_if_missing()

rather that the current (rather diverse) set of preambles.

Alternatively, we could maybe setup a custom PYTHONPATH, although that solution is brittle.

Here is an example of what can be put in practical_rl/__init__.py:

import logging
import os
import subprocess


def create_display_if_missing():
    display = os.environ.get('DISPLAY')
    if not isinstance(display, str) or len(display) == 0:
        logging.warning('No display detected (DISPLAY={}). Launching xvfb...'.format(display))
        subprocess.check_call(['../xvfb', 'start'])
        os.environ['DISPLAY'] = ':1'

[dniku]

Thinking a little more about this, there is a problem which must be addressed: in the current state, our notebooks are mostly standalone and can be run via Colab. The inclusion of a library will change that.