Flask框架如何让模型和数据同步[Flask框架]
使用ORM时,需要执行迁移操作以便在模型和持久化数据之间保持同步。我们使用Flask-Migrate这个扩展来完成该任务。
首先安装:
$ pip install flask-migrate$ pip install flask_script
然后在代码中引入:
from flask_script import Managerfrom flask_migrate import Migrate, MigrateCommand
进行必要的配置:
migrate = Migrate(app, db)manager = Manager(app)
manager.add_command('db', MigrateCommand)
运行管理器:
if __name__ == '__main__':manager.run()
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完整的代码如下:
from flask import Flaskfrom flask_sqlalchemy import SQLAlchemy
from flask_script import Manager
from flask_migrate import Migrate, MigrateCommand
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://localhost/appdb'db = SQLAlchemy(app)
migrate = Migrate(app, db)
manager = Manager(app)
manager.add_command('db', MigrateCommand)class Post(db.Model):
id = db.Column(db.Integer(), primary_key=True)
title = db.Column(db.String(80), unique=True)
post_text = db.Column(db.String(255))
def __init__(self, title, post_text):
self.title = title
self.post_text = post_text@app.route('/')def index():
return "Hello World"if __name__ == "__main__":
manager.run()
使用如下的命令初始化Alembic:
$ python app.py db initCreating directory /Users/Vihar/Desktop/flask-databases/migrations ... done
...
...
...
Generating /Users/Vihar/Desktop/flask-databases/migrations/alembic.ini ... done
执行第一个迁移任务:
$ python app.py db migrateINFO [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO [alembic.runtime.migration] Will assume transactional DDL.
INFO [alembic.autogenerate.compare] Detected added table 'post'Generating
/Users/Vihar/Desktop/flask-databases/migrations/versions/ed3b3a028447_.py ... done
一旦上述命令执行完毕,我们的数据表就会创建成功。现在更新数据库:
$ python app.py db upgrade
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