__init__.py

import os
import json
from flask import Flask
from flask_cors import CORS
from flask_swagger_ui import get_swaggerui_blueprint
from mlcraft.errors import connection_error, timeout_error
from werkzeug.exceptions import HTTPException
from requests.exceptions import ConnectionError, ConnectTimeout


def extract_config(file):
    configs = json.load(file)
    config = configs["py_server"]

    cpp = configs["cpp_server"]
    config["CPP_SERVER"] = f"http://{cpp['HOST']}:{cpp['PORT']}"

    client = configs["client"]
    config["CLIENT"] = f"http://{client['HOST']}:{client['PORT']}"

    config["SERVER_NAME"] = "localhost:3000"
    config["PREFERRED_URL_SCHEME"] = "http"

    return config


def make_app(config=None):
    app = Flask(__name__)
    # create a folder where the application will be launched
    try:
        os.makedirs(app.instance_path, exist_ok=True)
    except OSError as e:
        print(f"Failed to create an instance folder")
        raise e

    default_path = "../../config.json"
    config_path = os.environ.get("CONFIG_PATH")
    if config_path is None:
        print(f"CONFIG_PATH variable not set, using default path: {default_path}")
        config_path = default_path

    app.config.from_file(config_path, load=extract_config)
    if config is not None:
        app.config.update(config)

    # CORS(app, origins=app.config["CLIENT"])
    # uncomment this and comment line above if you want to make it simple
    CORS(app)

    swagger = get_swaggerui_blueprint(
        "/swagger",
        app.url_for("static", filename="swagger.yaml"),
    )
    app.register_blueprint(swagger, url_prefix="/swagger")

    from . import db  # this is ok, but only for professional programmers

    db.init_app(app)

    from .errors import Error, api_error, key_error, value_error, http_error

    app.register_error_handler(Error, api_error)
    app.register_error_handler(KeyError, key_error)  # no json field
    app.register_error_handler(ValueError, value_error)  # json wrong type
    app.register_error_handler(HTTPException, http_error)
    app.register_error_handler(TimeoutError, timeout_error)
    app.register_error_handler(ConnectTimeout, timeout_error)
    app.register_error_handler(ConnectionError, connection_error)

    from . import server

    app.register_blueprint(server.app)

    return app