Flask Academy · 课时

编写 create_app 函数

在工厂中构建并配置应用

编写 create_app 函数 是 CoddyKit 上的免费 Flask Academy 课时。这是第 2 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。

Meet the Factory

An application factory is just a function named create_app that builds a fresh Flask app, configures it, and returns it. No globals required. 🏭

The Smallest Factory

At its core, create_app creates the app inside the function body and returns it. Everything you used to do at module level moves in here.

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

Local, Not Global

Notice the app now lives as a local variable. Each call produces a brand new instance, so nothing leaks between tests or environments.

Configure Inside

Set configuration on the local app before returning it. A common move is app.config.from_object to load a settings class.

def create_app():
    app = Flask(__name__)
    app.config.from_object("config.Dev")
    return app

Accept a Config Argument

Make the factory flexible by accepting a config parameter. Pass Dev, Test, or Prod settings depending on how the app is launched.

def create_app(config_class):
    app = Flask(__name__)
    app.config.from_object(config_class)
    return app

Register Routes Inside

Define or import your routes within create_app so they attach to this specific instance, not a shared global.

def create_app():
    app = Flask(__name__)
    @app.route("/")
    def home():
        return "Hi"
    return app

Where to Put It

Place create_app in your package init, like app/__init__.py. Importers then call the factory instead of grabbing a global.

How Flask Finds It

The dev server looks for a callable named create_app automatically. Setting FLASK_APP to your package is usually enough to launch.

FLASK_APP=app flask run

A WSGI Entry Point

For production servers you expose one instance by calling the factory once in a small wsgi.py module.

from app import create_app
app = create_app()

Testing Gets Easy

Tests just call create_app with test config and get an isolated app every time. No shared state, no surprises. ✅

app = create_app("config.Test")

Keep It Focused

Treat create_app as an assembly line: create, configure, wire up, return. Resist stuffing business logic directly inside it.

Quick Check

What does a create_app factory function return?

Recap

You wrote create_app: a function that builds, configures, and returns a fresh Flask app. It replaces the global and makes config and testing simple. 🎯

常见问题解答

「编写 create_app 函数」课时是免费的吗？

是的 — 「编写 create_app 函数」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。

「编写 create_app 函数」这节课中我会学到什么？

在工厂中构建并配置应用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 2 节课，共 4 节。

「编写 create_app 函数」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。

此课程中的所有课时

← 返回 Flask Academy