MRE/app/__init__.py

from flask import Flask
import os
from logging import Logger, Formatter, getLogger, DEBUG, INFO, FileHandler


def load_config_from_environ(app: Flask) -> Flask:
    for env_var in os.environ.keys().filter(lambda x: x.startswith(app.name.upper())):
        config_name = env_var[len(app.name):]
        app.config[config_name] = os.environ[env_var]

    return app


def create_logger(app: Flask, log_level=INFO) -> None:
    logger = getLogger(__name__)
    formatter = Formatter(f'[%(asctime)s] {app.name.upper()} %(levelname)s: %(message)s (%(filename)s.%(funcName)s)')
    logger.setFormatter(formatter)
    logger.setLevel(log_level)
    to_file = FileHandler(os.environ.get('APP_LOG_PATH', f'./{app.name}.log'))
    logger.addHandler(to_file)

    app.logger = logger


def create_app() -> Flask:
    app = Flask(__name__)
    app = load_config_from_environ(app)
    create_logger(app)

    return app