Define and read env vars

env.py

"""
All environment variable access should be performed via this module.
- allows tracing of where variables are used
- provide sensible defaults
- reduce string typos

Declare env vars below with default values.
"""
import os
import sys
import ast

SIZE = 10
COLOR = 'red'

# Magic: Override locals with environment settings
for key, default_value in dict(locals()).items():
    if key in os.environ:
        if isinstance(default_value, str):
            setattr(sys.modules[__name__], key, os.getenv(key))
        else:
            setattr(sys.modules[__name__], key, ast.literal_eval(os.getenv(key)))

# function for doing this from an importing function
# Experimental: I'm not sure if this works yet, use the above to be sure
import os
import sys
import inspect 

def override_env_vars():
    """Override the variables in the module in which this function is called with 
    the values from Env vars, if they exist"""
    frm = inspect.stack()[1]
    mod = inspect.getmodule(frm[0])
    # mod is the python module from which this function is called:
    # https://stackoverflow.com/a/1095621/21188807

    # Magic: Override locals with environment settings
    if key in os.environ:
        if isinstance(default_value, str):
            setattr(sys.modules[mod.__name__], key, os.getenv(key))
        else:
            setattr(sys.modules[mod.__name__], key, ast.literal_eval(os.getenv(key)))
            

Credit to @ddrscott https://gist.github.com/ddrscott/bfb971845bf09cbb387e007addda5b8c