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读取和写入 request.session

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读取和写入 request.session 是 CoddyKit 上的免费 Django 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 Django Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Django 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。

The Session as a Dict

Think of request.session as a dictionary that follows one visitor. You read and write keys exactly like any Python dict.

Writing a Value

To remember something, just assign a key. Here we save a cart list so the visitor keeps their items across pages.

def add_to_cart(request):
    request.session['cart'] = [1, 2, 3]
    return redirect('cart')

Reading a Value

Read a key back the dictionary way. Using get with a default avoids a crash when the key has not been set yet.

cart = request.session.get('cart', [])

Updating Stored Data

To grow a cart, read it, change the Python object, then assign it back so Django notices the update and saves it.

cart = request.session.get('cart', [])
cart.append(7)
request.session['cart'] = cart

Mark It Modified

When you mutate a nested object in place, set session.modified to True so Django knows it must persist the change.

request.session['cart'].append(7)
request.session.modified = True

Deleting a Key

Remove a single value with del, just like a normal dictionary, to forget one piece of session state.

del request.session['cart']

Checking for a Key

Use the in operator to test whether a value exists before you read it, which keeps your view logic clean.

if 'cart' in request.session:
    show_cart()

What Can You Store

Session values must be JSON serializable by default. Lists, dicts, strings, and numbers are fine; model instances are not.

Clearing Everything

To wipe all session data for a visitor, call flush. It deletes the data and rotates the session key, handy at logout.

request.session.flush()

Set Expiry Per Session

Override the global timeout for one visitor with set_expiry. Passing zero ends the session when the browser closes.

request.session.set_expiry(0)

Saves Happen For You

You rarely call save yourself. The middleware writes the session at the end of each request whenever you changed it.

Quick Check

You changed a list already stored in the session in place. What must you do?

Recap

You used request.session like a dict: write, read with get, delete, flush, and set expiry. Remember to flag in-place edits as modified. Next up, the messages framework. 💬

常见问题解答

「读取和写入 request.session」课时是免费的吗？

是的 — 「读取和写入 request.session」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 Django Academy 课程的其余内容，请升级到 CoddyKit PRO。 Django Academy 课程共包含 4 节课。

「读取和写入 request.session」这节课中我会学到什么？

保存和获取购物车之类的值 你通过在浏览器中直接运行的动手代码来练习 Django 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 Django Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Django 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。

「读取和写入 request.session」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 Django Academy 课中编写并运行代码吗？

能。每节 Django 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

  1. 会话框架
  2. 读取和写入 request.session
  3. 消息框架
  4. Cookie 与会话对比
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