Flask中的數據庫遷移-SQLAlchemy

Question

flask-restplus和sqlalchemy設計我的后端。 我正在使用flask-migrate庫，以便在有任何此類要求時可以調整數據庫表。

這是我的目錄結構

-mainfolder/
     -app/
         -v1/
           -app.py
           -apis/
              -__init__.py
              -some folders.
               .
               .
               .
           -database/
              -__init__.py
              -models.py
           -config/
               -__init__.py
               -detect_config_file.py
            -

     -wsgi.py

我的app.py中的代碼是

import logging.config
import json
import os
import sys
from flask import Flask, Blueprint
from flask_restplus import Api
from flask_jwt_extended import JWTManager
from flask_cors import CORS
from database import *
from config.detect_config_file import config

app = Flask(__name__)
cors = CORS(app)
api = Api(version='1.0', title='Plug-n-Play APIs',
      description='Demostration of APIs behind plug-n-play dashboard')
logging_conf_path = 
 os.path.normpath(os.path.join(os.path.dirname(__file__), '../../logging.conf'))
 logging.config.fileConfig(logging_conf_path)
 log = logging.getLogger(__name__)

def configure_app(flask_app):

     flask_app.config['JWT_SECRET_KEY'] = config['JWT_SECRET_KEY']
     flask_app.config['JWT_BLACKLIST_ENABLED'] = config['JWT_BLACKLIST_ENABLED']
     flask_app.config['JWT_BLACKLIST_TOKEN_CHECKS'] = config['JWT_BLACKLIST_TOKEN_CHECKS']
     flask_app.config['SQLALCHEMY_DATABASE_URI'] = 'mysql+pymysql://'+ config['DB_USERNAME'] + ':' + config['DB_PASSWORD']+'@'+ config['DB_HOST'] + '/' + config['DB_NAME']
     flask_app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = config['DB_TRACK_MODIFICATIONS']


def initialize_app(flask_app):
   configure_app(flask_app)

    blueprint = Blueprint('api', __name__, url_prefix='/api/v1')
    api.init_app(blueprint)

    flask_app.register_blueprint(blueprint)

    db.init_app(flask_app)

    with flask_app.app_context():
      initDB()

    jwt = JWTManager(flask_app)


def main():
  initialize_app(app)
  log.info('>>>>> Starting development server <<<<<')
  app.run(debug=config['APP_DEBUG'], host="0.0.0.0")


if __name__ == "__main__":
  main()

數據庫文件夾中的models.py文件為

from database import db
#importing from __init__.py of database folder

from sqlalchemy.types import JSON
from sqlalchemy_utils.types.choice import ChoiceType
from config.detect_config_file import config
from flask_sqlalchemy import SQLAlchemy
from flask_script import Manager
from flask_migrate import Migrate, MigrateCommand
from app import app
#importing the flask app from app.py 

 db = SQLAlchemy(app)
 migrate = Migrate(app, db)

 manager = Manager(app)
 manager.add_command('db', MigrateCommand)

class UserModel(db.Model):
    __tablename__ = 'users'

    id = db.Column(db.Integer, primary_key = True)
    username = db.Column(db.String(120), unique = True, nullable = False)

if __name__ == '__main__':
    manager.run()

數據庫文件夾中的__init__.py文件是

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()


def initDB():
    from database.models import *
    db.create_all()

我在這里的思考過程是，當我運行app.py時，它將在數據庫中創建表（我已經在mysql中創建了數據庫）app.py中的代碼段

with flask_app.app_context():
   initDB()

當模式更改時，在這種情況下，我將運行這些命令來更新數據庫，而不必刪除數據庫並重新創建。

$python models.py db init
$python models.py db migrate
$python models.py db upgrade

但這是行不通的。 當我嘗試從 models.py中的應用程序導入應用程序時，出現循環依賴項錯誤

請查看我的代碼，並告訴我我的方法是否正確或有更好的方法來執行此操作。 我的主要目標是像在django中一樣實現數據庫遷移，以便我可以輕松更改數據庫架構。

Answer 1

我建議在app / init.py中實例化兩個app / db，以便可以從單個位置導入app / db。 實例化管理器后，將管理器導入到app目錄之外的run.py中，並在app.run（）/ manager.run（）之間進行切換

模型

from app import db
class UserModel(db.Model):
    __tablename__ = 'users'

    id = db.Column(db.Integer, primary_key = True)
    username = db.Column(db.String(120), unique = True, nullable = False)

項目/應用程序/ init .py

def create_app():
    app = Flask(__name__)
    return app

app = create_app()
# import this db to your model.
db = SQLAlchemy(app)
manager = Manager(app)
manager.add_command('db', MigrateCommand)

項目/ run.py

# Placed from app import manager right above main block.
from app import manager

if __name__ == '__main__':
    # switch between run/manager based on your need.
    #manager.run() # for DB migration
    app.run(threaded=True, debug=True)