使用模板获取错误信息

1、index.html

<form action="" method="post">
  <table>
    <tbody>
    <tr>
      <td>用户名：</td>
      <td><input type="text" name="username"></td>
    </tr>
    <tr>
      <td>密码：</td>
      <td><input type="password" name="password"></td>
    </tr>
    <tr>
      <td>重复密码：</td>
      <td><input type="password" name="repassword"></td>
    </tr>
    <tr>
      <td></td>
      <td><input type="submit" value="立即注册"></td>
    </tr>
    </tbody>
  </table>
</form>
{% for error in form.username.errors %}
  <p>{{ error }}</p>
{% endfor %}
{% for error in form.password.errors %}
  <p>{{ error }}</p>
{% endfor %}
{% for error in form.repassword.errors %}
  <p>{{ error }}</p>
{% endfor %}

2、app.py

from flask import Flask, render_template, request
from wtforms import Form, StringField, PasswordField
from wtforms.validators import Length, EqualTo

class RegForm(Form):
    username = StringField(validators=[
        Length(min=6, max=12, message='用户名需要输入6到12个字符')
    ])
    password = PasswordField(validators=[
        Length(min=6, max=12, message='密码需要输入6到12个字符')
    ])
    repassword = PasswordField(validators=[
        EqualTo('password', message='两次输入的密码需要相同')
    ])

app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def index():
    form = RegForm(request.form)
    if request.method == 'GET':
        return render_template('index.html', form=form)
    else:
        if form.validate():
            return '注册成功'
        else:
            return render_template('index.html', form=form)

if __name__ == '__main__':
    app.run()