6.2 使用WTForms

#### 6.2.1 安装WTForms

WTForms是一个功能强大的表单处理库，支持多种验证器和字段类型。安装WTForms的Flask扩展：

bash复制

```bash
pip install Flask-WTF
```

#### 6.2.2 定义表单

使用WTForms定义表单类，每个表单字段对应一个表单类的属性。

Python复制

```python
from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, SubmitField
from wtforms.validators import DataRequired, Length, Email

class LoginForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired(), Length(min=4, max=20)])
    password = PasswordField('Password', validators=[DataRequired(), Length(min=6, max=35)])
    submit = SubmitField('Login')
```

#### 6.2.3 使用表单

在视图函数中使用表单，并在模板中渲染表单。

Python复制

```python
from flask import render_template, flash, redirect, url_for
from forms import LoginForm

@app.route('/login', methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        flash('Login requested for user {}, remember_me={}'.format(
            form.username.data, form.remember_me.data))
        return redirect(url_for('index'))
    return render_template('login.html', title='Sign In', form=form)
```

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