安装并配置扩展
设置数据库 URI 并初始化 SQLAlchemy
安装并配置扩展 是 CoddyKit 上的免费 Flask Academy 课时。 这是第 1 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Flask Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Flask Academy 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
Why an ORM at All
Writing raw SQL by hand gets messy fast. An ORM lets you work with Python objects and rows feel like normal classes. 🗃️
Meet Flask-SQLAlchemy
Flask-SQLAlchemy is the official extension that wires SQLAlchemy into Flask, so your app gets a clean, ready-to-use database layer.
Install the Package
You add it like any dependency. pip pulls in Flask-SQLAlchemy and the SQLAlchemy core it builds on automatically.
pip install Flask-SQLAlchemyCreate the db Object
You make one SQLAlchemy instance, usually named db. Every model and query you write later will hang off this single object.
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()The Database URI
Flask needs to know where your data lives. The SQLALCHEMY_DATABASE_URI setting is a connection string pointing at your database.
A Simple SQLite URI
For learning, SQLite is perfect: it lives in one file, needs no server, and the URI is just a path on disk.
app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///app.db"Bind db to the App
After config, you connect the extension to your app with init_app. This hands Flask-SQLAlchemy everything it needs to run.
db.init_app(app)Two Ways to Initialize
You can pass the app straight to SQLAlchemy(app) for tiny apps, or use init_app later to keep db reusable across setups.
Swap Databases Easily
Only the URI changes between SQLite, PostgreSQL, or MySQL. Your models and queries stay identical, which makes switching painless.
"postgresql://user:pass@localhost/mydb"Skip the Modification Tracker
Set SQLALCHEMY_TRACK_MODIFICATIONS to False. It silences a warning and avoids extra overhead you almost never need.
app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = FalseOne Extension, Many Tools
Once configured, db gives you Model for tables, Column for fields, and session for saving. You will meet each of these soon.
Quick Check
Which config key tells Flask-SQLAlchemy where your database lives?
Recap
You installed the extension, created a db object, set the URI, and bound it with init_app. Your app is ready for models. 🎉
常见问题解答
「安装并配置扩展」课时是免费的吗？
是的 — 「安装并配置扩展」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Flask Academy 课程的其余内容，请升级到 CoddyKit PRO。 Flask Academy 课程共包含 4 节课。
「安装并配置扩展」这节课中我会学到什么？
设置数据库 URI 并初始化 SQLAlchemy 你通过在浏览器中直接运行的动手代码来练习 Flask Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Flask Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Flask Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 1 节课，共 4 节。
「安装并配置扩展」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Flask Academy 课中编写并运行代码吗？
能。每节 Flask Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。