Python form.validate_on_submit() 始终为假

Question

我正在使用 flask_wtf

这是我的登录表单

from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, BooleanField, SubmitField
from wtforms.validators import DataRequired, Length


class LoginForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired()])
    password = PasswordField('Password', validators=[DataRequired(), Length(8, 128)])
    remember = BooleanField('Remember me')
    submit = SubmitField('Log in')

这是我的 login.html:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>login</title>
</head>
<body>
<form method="POST" action="">
    {{ form.csrf_token }}
    {{ form.username.label }}<br>{{ form.username }}<br>
    {{ form.password.label }}<br>{{ form.password }}<br>
    {{ form.remember }}{{ form.remember.label }}<br>
    {{ form.submit }}<br>
</form>
</body>
</html>

和我的app.py

from flask import Flask, render_template
from forms import LoginForm

app = Flask(__name__)
app.secret_key = 'learnflask'
@app.route('/login', methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        username = form.username.data
        print(username)
    return render_template('login.html', form=form)


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

我的问题是用户名不打印。似乎登录表单未提交，form.validate_on_submit() 是错误的。

Answer 1

form.validate_on_submit() 是错误的，因为您还没有将 request.form 对象添加到 LoginForm()

form = LoginForm(request.form)

Answer 2

对于 password 字段，您已将验证器设置为检查长度是否在 8 到 128 之间。如果用户提供的密码长度更小或更长，验证将失败。我认为这就是 form.validate_on_submit() 总是错误的原因。

我已经在模板中显示了错误信息并得到了错误。

login.html:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>login</title>
    <style>
        .validation_error{
        color: red;
    }
    </style>
</head>
<body>
<form method="POST" action="">
    {{ form.csrf_token }}
    {{ form.username.label }}<br>{{ form.username }}<span class="validation_error">{{ ', '.join(form.username.errors) }}</span><br>
    {{ form.password.label }}<br>{{ form.password }}<span class="validation_error">{{ ', '.join(form.password.errors) }}</span><br>
    {{ form.remember }}{{ form.remember.label }}<span class="validation_error">{{ ', '.join(form.remember.errors) }}</span><br>
    {{ form.submit }}<br>
</form>
</body>
</html>

app.py:

from flask import Flask, render_template
from forms import LoginForm

app = Flask(__name__)
app.secret_key = 'learnflask'
@app.route('/login', methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        username = form.username.data
        return username
    return render_template('login.html', form=form)

输出：

有效输入：

输入无效：

Python form.validate_on_submit() 始终为假

Python form.validate_on_submit() always false

python

flask

flask-wtforms