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设置并读取 session 字典

在多个请求间存储每个用户的数据

设置并读取 session 字典 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 Sessions Exist

HTTP forgets you after every request. A session lets your Flask app remember a single user across many requests. 🧠

It Feels Like a Dict

Flask gives you a session object that behaves just like a Python dictionary. You read and write keys on it as usual.

from flask import session

Import It First

You always pull session straight from flask. It is a special proxy that points at the current user's session for you.

from flask import Flask, session

Write a Value

To store data, assign a key on session. Here we remember who is logged in for this visitor.

@app.route('/login')
def login():
    session['user'] = 'ada'
    return 'Saved!'

Read It Back

On a later request you read the same key from session, and the value is still there for that user.

@app.route('/me')
def me():
    return session['user']

Read Safely with get

Use session.get instead of brackets so a missing key returns None rather than raising a KeyError.

name = session.get('user', 'guest')

Check If a Key Is There

You can test membership too. The in operator tells you whether a value was ever stored for this user.

if 'user' in session:
    print('known visitor')

Remove One Value

Logging out usually means dropping a key. Use session.pop with a default so it never errors when absent.

session.pop('user', None)

Clear Everything

To wipe the whole session in one call, use session.clear. Every stored key for that user is gone.

session.clear()

Per User, Not Global

Each browser gets its own session. What you store for one visitor never leaks into another person's session.

Keep It Small

Store only tiny markers like a user id, not big objects. The session rides along with every request, so size matters.

Quick Check

You want to read a session value without crashing if it is missing.

Recap

You learned that session is a per-user dict: set keys to save data, read with get, and clear to log out. Nice work! 🎉

常见问题解答

「设置并读取 session 字典」课时是免费的吗？

是的 — 「设置并读取 session 字典」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。

「设置并读取 session 字典」这节课中我会学到什么？

在多个请求间存储每个用户的数据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。

「设置并读取 session 字典」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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