Python/Flask ImportError：尝试在没有已知父包的情况下进行相对导入

Question

I keep running into this ImportError in my Flask app not really understanding why it's happening:

server      | Traceback (most recent call last):
server      |   File "/app/app.py", line 9, in <module>
server      |     from .models import db, Properties, Usage
server      | ImportError: attempted relative import with no known parent package

In app.py I have the following:

from .models, import db
from . import config

APP = flask.Flask(__name__)
cors = CORS(APP)

APP.config['SQLALCHEMY_DATABASE_URI'] = config.DATABASE_CONNECTION_URI
APP.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
APP.app_context().push()
db.init_app(APP)
db.create_all()

Where my file tree looks like:

|- server
   |
   |- app.py
   |- config.py
   |- models.py

config.py looks like:

import os

user = os.environ['POSTGRES_USER']
password = os.environ['POSTGRES_PASSWORD']
host = os.environ['POSTGRES_HOST']
database = os.environ['POSTGRES_DB']
port = os.environ['POSTGRES_PORT']

DATABASE_CONNECTION_URI = f'postgresql+psycopg2://{user}:{password}@{host}:{port}/{database}'

What should I do to fix this?

EDIT: forgot to mention, I'm using a docker-compose.yml file to build my database (as well as the rest of my application):

version: "3.9"
services:
    server:
        container_name: server
        build: ./server
        ports:
            - "80:5000"
        volumes:
            - ./server:/app
        environment:
            FLASK_ENV: development
        env_file: 
            - ./.env
    web:
        build: ./app
        ports:
            - "3000:3000"
        volumes:
            - ./app:/user/src/app
        depends_on: 
            - server
    database:
        container_name: postgres
        image: postgres:latest
        env_file: ./server/database.conf
        ports:
            - 5432:5432
        volumes:
            - db_volume:/var/lib/postgresql

volumes:
    db_volume:

Answer 1

A simple mistake: It will be:

from models import db
import config
APP = flask.Flask(__name__)
cors = CORS(APP)
APP.config['SQLALCHEMY_DATABASE_URI'] = config.DATABASE_CONNECTION_URI
APP.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
APP.app_context().push()
db.init_app(APP)
db.create_all()