python之Flask : UndefinedError: 'form' is undefined 中的 WTForms

我是 Flask 和 WTForms 的新手，我无法呈现我的 HTML 页面。翻了一遍WTforms的文档，还是找不到错误的来源:

jinja2.exceptions.UndefinedError, UndefinedError: 'form' is undefined 

我的代码如下:

表单.py

from flask.ext.wtf import Form 
from wtforms import TextField, BooleanField, TextAreaField, StringField, PasswordField, SelectField, validators 
 
class LoginForm(Form): 
    username = TextField('Username', [ 
        validators.Required(),  
        validators.Length(min=4, max=25) 
    ]) 
    password = PasswordField('New Password', [ 
        validators.Required() 
    ]) 

app.py

from forms import * 
from wtforms import Form, fields, BooleanField, TextField, StringField,     PasswordField, validators 
from werkzeug.security import generate_password_hash, \ 
 check_password_hash 
 
@app.route('/login/', methods=['GET', 'POST']) 
def login(): 
    form = LoginForm(request.form) 
    if request.method == 'POST' and form.validate(): 
        if load_user(form.username.data) is None: 
            flash('Invalid username') 
        else:  
            if check_password_hash(cred.password, form.password.data): 
                return redirect(url_for('browse'))   
            else:  
                flash('Invalid password') 
    return render_template('login.html', title='Login', form=form) 

login.html

{% extends "base.html" %} 
{% block body %} 
    <form action="{{ url_for('login') }}" method="Post"> 
        <fieldset> 
            <div>{{ form.username.label }}: {{ form.username() }}</div> 
            <div>{{ form.password.label }}: {{ form.password() }}</div> 
            <div class="form-group"> 
                <button class="btn btn-default" type="submit"> 
                    <span aria-hidden="true" class="glyphicon glyphicon-log-in"></span> 
                    Log In 
                </button> 
            </div> 
        </fieldset> 
    </form>     
    <div> 
    or <a href="new">Register</a> for an account 
    </div> 
{% endblock %} 

请您参考如下方法:

您仍然必须使用 return 语句 - 例如:

return render_template('login.html', title='Login', form=form) 

在所有的 if-else 分支中，否则，form 上下文变量不会传递给模板。 login 函数应该如下所示:

@app.route('/login/', methods=['GET', 'POST']) 
def login(): 
    form = LoginForm(request.form) 
    if request.method == 'POST' and form.validate(): 
        if load_user(form.username.data) is None: 
            flash('Invalid username') 
            return render_template('login.html', title='Login', form=form) 
    else:  
        if check_password_hash(cred.password, form.password.data): 
            return redirect(url_for('browse'))   
        else:  
            flash('Invalid password') 
            return render_template('login.html', title='Login', form=form) 
    return render_template('login.html', title='Login', form=form)