Django Academy · 课时

is_valid 与 cleaned_data

验证输入并读取清理后的值

is_valid 与 cleaned_data 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。

Bind Data First

To validate, create a bound form by passing the submitted data into it. Only bound forms can be validated.

form = ContactForm(request.POST)

Call is_valid()

is_valid() runs every field validation and returns True only if all of them pass. It triggers the whole cleaning process.

if form.is_valid():
    handle(form)

cleaned_data Appears

After is_valid() returns True, Django fills cleaned_data, a dict of validated, type-converted values ready to use.

name = form.cleaned_data["name"]

Values Are Converted

Cleaning converts types too. An IntegerField gives you a real int, and a DateField gives you a Python date, not raw strings.

age = form.cleaned_data["age"]  # int

Errors Collect Automatically

If validation fails, the messages land in form.errors, keyed by field name so you can show each problem clearly.

if not form.is_valid():
    print(form.errors)

Field-Level clean Methods

Add a method named clean_field to validate one field and return its cleaned value. Raise ValidationError to reject it.

def clean_name(self):
    name = self.cleaned_data["name"]
    return name.strip()

Raise ValidationError

Inside a clean method, raise ValidationError with a message to reject the value and attach an error to that field.

if "@" not in email:
    raise forms.ValidationError("Bad email")

Form-Wide clean()

Override clean() to validate fields against each other, like confirming two passwords match across the whole form.

def clean(self):
    cleaned = super().clean()
    return cleaned

Cross-Field Checks

In clean() you can read several cleaned_data keys and raise an error when their combination is invalid.

if start > end:
    raise forms.ValidationError("Bad range")

The Cleaning Order

Django runs field cleaning first, then your form-wide clean(). So clean() can safely rely on already-validated field values.

Use cleaned_data Safely

Always read input from cleaned_data, never from request.POST. Only cleaned_data holds validated, converted, trusted values.

email = form.cleaned_data["email"]

Quick Check

Test your grip on validation.

Recap

Bind data, call is_valid(), then read trusted values from cleaned_data. Use clean methods to add your own rules. ✅

常见问题解答

「is_valid 与 cleaned_data」课时是免费的吗？

是的 — 「is_valid 与 cleaned_data」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。

「is_valid 与 cleaned_data」这节课中我会学到什么？

验证输入并读取清理后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。

「is_valid 与 cleaned_data」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。

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