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定义 FlaskForm 类

在 Python 中声明字段和验证器

定义 FlaskForm 类 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 Flask-WTF

Handling raw form data by hand gets messy fast. Flask-WTF lets you declare a form once as a Python class and reuse it everywhere. 🎯

Install the Extension

Flask-WTF wraps the WTForms library and adds CSRF protection. Install it with pip before you write a single field.

pip install Flask-WTF

Subclass FlaskForm

Every form you build is a class that inherits from FlaskForm. That base class gives you CSRF and validation for free.

from flask_wtf import FlaskForm

class LoginForm(FlaskForm):
    pass

Add Your First Field

Fields are class attributes set to field objects. A StringField renders as a text input and stores whatever the user types.

from wtforms import StringField

class LoginForm(FlaskForm):
    username = StringField('Username')

Common Field Types

WTForms ships many field types. Reach for PasswordField, BooleanField, or SelectField so each input matches the data you expect.

from wtforms import PasswordField, BooleanField

password = PasswordField('Password')
remember = BooleanField('Remember me')

Give Fields a Label

The first argument to a field is its label. That text is what your template shows next to the input, so make it human-friendly.

email = StringField('Email address')

Attach Validators

Pass a validators list to enforce rules. DataRequired refuses an empty submission before your view ever runs.

from wtforms.validators import DataRequired

username = StringField('Username', validators=[DataRequired()])

Stack Multiple Rules

Validators run in order, so you can stack them. Require a value, then check its length, all in one field.

from wtforms.validators import DataRequired, Length

name = StringField('Name', validators=[DataRequired(), Length(min=2, max=40)])

Add a Submit Button

A SubmitField becomes the form button. Including it in the class keeps the whole form definition in one tidy place.

from wtforms import SubmitField

submit = SubmitField('Log in')

A Complete Form Class

Put the pieces together and you have a reusable, self-validating form class ready to instantiate in any view.

class LoginForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired()])
    password = PasswordField('Password', validators=[DataRequired()])
    submit = SubmitField('Log in')

Instantiate in a View

Inside a view you simply create an instance. The form object then carries the fields, data, and errors for that request.

@app.route('/login')
def login():
    form = LoginForm()
    return render_template('login.html', form=form)

Quick Check

Which base class should your Flask-WTF forms inherit from?

Recap

You defined a form as a class: subclass FlaskForm, add typed fields with labels and validators, and finish with a submit button. Reusable and clean. ✨

常见问题解答

「定义 FlaskForm 类」课时是免费的吗？

是的 — 「定义 FlaskForm 类」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。

「定义 FlaskForm 类」这节课中我会学到什么？

在 Python 中声明字段和验证器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。

「定义 FlaskForm 类」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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