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current_app 与 g 对象

访问当前应用和每个请求的存储空间

第 2 / 4 课13 个步骤

current_app 与 g 对象 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 current_app

current_app is a proxy that always points to the app handling the work right now. Import it whenever you need the active application.

from flask import current_app

Why Not Import app?

Importing your app object directly causes circular imports as projects grow. current_app sidesteps that by resolving the app at runtime.

Reading Config

A common use is reading settings: current_app.config gives you the active app's configuration without importing the app module.

key = current_app.config["SECRET_KEY"]

It Needs a Context

current_app only works while an app context is active. Inside a view that is automatic, since the request pushed one for you.

Meet the g Object

g is a simple scratchpad for one request. Attach anything to it and read it back later in the same request.

from flask import g
g.user = "alice"

g Is Per Request

The g object is reset for every request. Data you stash on it never leaks into another visitor's request.

A Typical g Use

Use g to share work across functions in one request, like caching the current user so you fetch it from the database only once.

if "db" not in g:
    g.db = connect()

g Is Not Storage

Do not treat g as a database. It forgets everything the moment the request ends, so use it only for that request's lifetime.

g Lives in the App Context

Surprisingly, g belongs to the app context, not the request context. In practice both exist during a request, so it just works.

Cleaning Up With g

Pair g with teardown handlers to close what you opened, like closing a database connection after the response is sent.

@app.teardown_appcontext
def close(exc):
    g.pop("db", None)

current_app and g Together

They pair nicely: read settings from current_app, then stash request-specific results on g so the rest of the request can reuse them.

Quick Check

Let us pin down what g is for.

在交互式课程中回答

Recap

Two handy proxies: current_app finds the active app and its config, while g is a per-request scratchpad you wipe clean each time. 🎉

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常见问题解答

「current_app 与 g 对象」课时是免费的吗？

是的 — 「current_app 与 g 对象」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。

「current_app 与 g 对象」这节课中我会学到什么？

访问当前应用和每个请求的存储空间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。

「current_app 与 g 对象」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。

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