Python flask路由不能很好地处理引导模式表单，生成表单未定义错误

在测试我页面的“登录失败”错误消息部分时，我经常会收到一个表单未定义的jinja错误。我对使用Python/Flask编码以及使用引导模式和表单非常陌生，所以我确信这是我一直在寻找的简单的东西。因为我使用的是modals，所以我需要在python代码中向每个页面路由添加命令，我觉得错误就在我使用的嵌套If中

我尝试过移动Flask代码，以便首先运行登录部分，但无论我尝试什么，都会出现相同的错误。我能够使用已知的、良好的用户名/密码登录，并且我可以毫无问题地注册新用户名。如果这些信息太多，我很抱歉，我以前没有在这里发布过，但我经常使用这些信息进行故障排除，因此我有一种很好的感觉，这里的社区可以发现我做错了什么

这是Python

#Define routes
@app.route('/home', methods=['GET', 'POST'])
def index():
    #Allow registry from page
    form = RegisterForm(request.form)
    if request.method == 'POST' and form.validate():
        name = form.name.data
        email = form.email.data
        username = form.username.data
        password = sha256_crypt.encrypt(str(form.password.data))

        # Execute query
        engine.execute("INSERT INTO users(name, email, username, password) VALUES(?, ?, ?, ?)", (name, email, username, password))
        # Changes Auto Commit so there is no need for opening a session or running a commit line.

        flash('You are now registered and can log in', 'success')

        return redirect(url_for('index'))
    else:
         #Allow login from page
        if request.method == 'POST':
            # Get Form Fields
            username = request.form['username']
            password_candidate = request.form['password']
            # Get user by username
            result = engine.execute("SELECT Username, Password FROM users WHERE username = ?", [username])

            # Get stored hash
            data = result.fetchone()
            if data is None:
                error = 'Username not found'
                return render_template('home.html', error=error)

            password = data['Password']

            # Compare Passwords
            if sha256_crypt.verify(password_candidate, password):
                # Passed
                session['logged_in'] = True
                session['username'] = username

                flash('You are now logged in', 'success')

                return redirect(url_for('dashboard'))
            else:
                error = 'Invalid login'
            return render_template('home.html', error=error)
    return render_template('home.html', form=form)

这是HTML

<nav class="navbar navbar-expand-lg navbar-dark bg-dark">
    <a class="navbar-brand" href="#"><img src="/static/images/kissclipart-sti-logo2.png"></a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  </button>
    {% if session.logged_in %}
    <div class="collapse navbar-collapse" id="navbarSupportedContent">
      <ul class="navbar-nav mr-auto">
        <li class="nav-item">
          <a class="nav-link" href="/home"><i class="fas fa-home"></i> Home <span class="sr-only">(current)</span></a>
        </li>
        <li class="nav-item">
          <a class="nav-link" href="/about"><i class="fas fa-chalkboard"></i> About Us</a>
        </li>
        <li class="nav-item">
          <a class="nav-link" href="/articles"><i class="fas fa-book"></i> Articles</a>
        </li>
        <li class="nav-item dropdown">
          <a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
            Dropdown
          </a>
          <div class="dropdown-menu" aria-labelledby="navbarDropdown">
            <a class="dropdown-item" href="#">Action</a>
            <a class="dropdown-item" href="#">Another action</a>
            <div class="dropdown-divider"></div>
            <a class="dropdown-item" href="#">Something else here</a>
          </div>
        </li>
      </ul>
      {% else %}
      <div class="collapse navbar-collapse" id="navbarSupportedContent">
          <ul class="navbar-nav mr-auto">
            <li class="nav-item">
              <a class="nav-link" href="/home"><i class="fas fa-home"></i> Home <span class="sr-only">(current)</span></a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="/about"><i class="fas fa-chalkboard"></i> About Us</a>
            </li>
          </ul>
      {% endif %}
      <ul class="navbar-nav navbar-right">
      {% if session.logged_in %}
      <li class="nav-item">
     <!--   <button type="button" class="btn btn-secondary" onclick="window.location.href='/dashboard'"><i class="fas fa-tachometer-alt"></i> Dashboard</a></li> -->
          <a class="nav-link" href="/dashboard"><i class="fas fa-tachometer-alt"></i> Dashboard </a>
      <li class="nav-item">
      <!-- LogOut Modal Button -->
  <!-- <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#Logout_Modal"><i class="fas fa-sign-out-alt"></i> 
        Log out
      </button> -->
      <a class="nav-link" data-toggle="modal" data-target="#Logout_Modal" href="#Logout_Modal"><i class="fas fa-sign-out-alt"></i> Logout </a>
      <!-- Modal -->
      <div class="modal fade" id="Logout_Modal" tabindex="-1" role="dialog" aria-labelledby="Logout_ModalLabel" aria-hidden="true">
        <div class="modal-dialog" role="document">
          <div class="modal-content">
            <div class="modal-header">
              <h5 class="modal-title" id="Logout_ModalLabel">Log out?</h5>
              <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                <span aria-hidden="true">&times;</span>
              </button>
            </div>
            <div class="modal-body">
              Are you sure you want to logout?
            </div>
            <div class="modal-footer">
              <button type="button" class="btn btn-outline-danger" data-dismiss="modal">No, still working!</button>
              <button type="button" class="btn btn-outline-success" onclick="window.location.href='/logout';">Yup, all done!</button>
            </div>
          </div>
        </div>
      </div>
    </ul>
    <form class="form-inline my-2 my-lg-0">
      <input class="form-control mr-sm-2" type="search" placeholder="Search" aria-label="Search">
      <button class="btn btn-outline-success my-2 my-sm-0" type="submit">Search</button>
    </form>
  </div>
</nav>
        {% else %}
        <li class="nav-item mr-auto">
        <!-- Register Modal Button -->
        <button type="button" class="btn btn-outline-success" data-toggle="modal" data-target="#Register_Modal"><i class="fas fa-user-plus"></i>
            Register?
          </button>
          <!-- Modal -->
          <div class="modal fade" id="Register_Modal" role="dialog" aria-labelledby="Register_ModalLabel" aria-hidden="true">
            <div class="modal-dialog" role="document">
              <div class="modal-content">
                <div class="modal-header">
                  <h5 class="modal-title" id="Register_ModalLabel">Let's get registered!</h5>
                  <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                    <span aria-hidden="true">&times;</span>
                  </button>
                </div>
                <div class="modal-body">
                    <h1>Register</h1>
                    {% from "includes/_formhelpers.html" import render_field %}
                    <form method="POST" action="">
                      <div class="form-group">
                        {{render_field(form.name, class_="form-control")}}
                      </div>
                      <div class="form-group">
                        {{render_field(form.email, class_="form-control")}}
                      </div>
                      <div class="form-group">
                        {{render_field(form.username, class_="form-control")}}
                      </div>
                      <div class="form-group">
                        {{render_field(form.password, class_="form-control")}}
                        <p>Your Password is required to be 6 characters long, a strong password is suggested. Please see the example below</p>
                        <p>Ex: Th1s1s@cceptabl3!</p>
                      </div>
                      <div class="form-group">
                        {{render_field(form.confirm, class_="form-control")}}
                      </div>
                      <p><input type="submit" class="btn btn-outline-success" value="Submit"></p>
                      <button type="button" class="btn btn-outline-danger" data-dismiss="modal">No, I changed my mind!</button>
                    </form>
                </div>
                <div class="modal-footer justify-content-between">
                    <div mr-auto> Already a member? <a href="#" data-toggle="modal" data-target="#Login_Modal" data-dismiss="modal">  Sign in here!</a></div>
              </div>
            </div>
          </div>

        <li class="nav-item mr-auto">
          <!-- Login Modal Button -->
          <button type="button" class="btn btn-outline-light" data-toggle="modal" data-target="#Login_Modal"><i class="fas fa-sign-in-alt"></i> 
            Login
            </button>
            <!-- Modal -->
            <div class="modal fade" id="Login_Modal"  role="dialog" aria-labelledby="Login_ModalLabel" aria-hidden="true">
              <div class="modal-dialog" role="document">
                <div class="modal-content">
                  <div class="modal-header">
                    <h5 class="modal-title" id="Login_ModalLabel">Ready to log in?</h5>
                    <button type="button" class="close" data-dismiss="modal" aria-label="Close">
                      <span aria-hidden="true">&times;</span>
                    </button>
                  </div>
                  <div class="modal-body">
                      <form action="" method="POST">
                          <div class="form-group">
                            <label>Username</label>
                            <input type="text" name="username" required placeholder="JSmith" autofocus="autofocus" class="form-control" value={{request.form.username}}>
                          </div>
                          <div class="form-group">
                            <label>Password</label>
                            <input type="password" name="password" required class="form-control" value={{request.form.password}}>
                          </div>
                          <button type="submit" class="btn btn-outline-success">Login!</button>
                          <button type="button" class="btn btn-outline-danger" data-dismiss="modal">Not right now</button>
                        </form>
                  </div>
                  <div class="modal-footer justify-content-between">
                    <div mr-auto> Not a member? <a href="#" data-toggle="modal" data-target="#Register_Modal" data-dismiss="modal">  Sign up here!</a></div>
                  </div>
                </div>
              </div>
            </div>
          </li>
      {% endif %}
    </ul>
  </div>
</nav>

{%if session.logged_in%}










{%else%}






{%endif%}

{%if session.logged_in%}


注销？
&时代；
您确定要注销吗？
不，还在工作！
是的，全部完成！

搜寻
{%else%}

登记
让我们注册吧！
&时代；
登记
{%来自“includes/_formhelpers.html”导入呈现字段%}
{{render_字段（form.name，class=“form control”）}
{{render_字段（form.email，class=“form control”）}
{{render_字段（form.username，class=“form control”）}
{{render_字段（form.password，class=“form control”）}
您的密码长度要求为6个字符，建议使用强密码。请参见下面的示例

例：Th1s1s@cceptabl3!

{{render_字段（form.confirm，class=“form control”）}

不，我改变主意了！
已经是会员了？

登录
准备好登录了吗？
&时代；
用户名
密码
登录！
现在不行
不是会员？

{%endif%}

下面是我得到的错误：

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

Traceback (most recent call last)
File "C:\ProgramData\CooperConda\lib\site-packages\flask\app.py", line 2463, in __call__
return self.wsgi_app(environ, start_response)
File "C:\ProgramData\CooperConda\lib\site-packages\flask\app.py", line 2449, in wsgi_app
response = self.handle_exception(e)
File "C:\ProgramData\CooperConda\lib\site-packages\flask\app.py", line 1866, in handle_exception
reraise(exc_type, exc_value, tb)
File "C:\ProgramData\CooperConda\lib\site-packages\flask\_compat.py", line 39, in reraise
raise value
File "C:\ProgramData\CooperConda\lib\site-packages\flask\app.py", line 2446, in wsgi_app
response = self.full_dispatch_request()
File "C:\ProgramData\CooperConda\lib\site-packages\flask\app.py", line 1951, in full_dispatch_request
rv = self.handle_user_exception(e)
File "C:\ProgramData\CooperConda\lib\site-packages\flask\app.py", line 1820, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "C:\ProgramData\CooperConda\lib\site-packages\flask\_compat.py", line 39, in reraise
raise value
File "C:\ProgramData\CooperConda\lib\site-packages\flask\app.py", line 1949, in full_dispatch_request
rv = self.dispatch_request()
File "C:\ProgramData\CooperConda\lib\site-packages\flask\app.py", line 1935, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "C:\Users\tlquickl\devel\MyFlaskApp\app.py", line 61, in index
return render_template('home.html', error=error)
File "C:\ProgramData\CooperConda\lib\site-packages\flask\templating.py", line 140, in render_template
ctx.app,
File "C:\ProgramData\CooperConda\lib\site-packages\flask\templating.py", line 120, in _render
rv = template.render(context)
File "C:\ProgramData\CooperConda\lib\site-packages\jinja2\asyncsupport.py", line 76, in render
return original_render(self, *args, **kwargs)
File "C:\ProgramData\CooperConda\lib\site-packages\jinja2\environment.py", line 1008, in render
return self.environment.handle_exception(exc_info, True)
File "C:\ProgramData\CooperConda\lib\site-packages\jinja2\environment.py", line 780, in handle_exception
reraise(exc_type, exc_value, tb)
File "C:\ProgramData\CooperConda\lib\site-packages\jinja2\_compat.py", line 37, in reraise
raise value.with_traceback(tb)
File "C:\Users\tlquickl\devel\MyFlaskApp\templates\home.html", line 1, in top-level template code
{% extends 'layout.html' %}

{% block body %}
  <div class="center">
    <div class="jumbotron text-center">
        <h1>Welcome to My FlaskApp</h1>
File "C:\Users\tlquickl\devel\MyFlaskApp\templates\layout.html", line 23, in top-level template code

    <script type="text/javascript">
        CKEDITOR.replace('editor')
    </script>

    {% include 'includes/_navbar.html' %}
    <div class="container">
        {% include 'includes/_messages.html' %}
        {% block body %}{% endblock %}
    </div>
<script>
File "C:\Users\tlquickl\devel\MyFlaskApp\templates\includes\_navbar.html", line 100, in top-level template code
                <div class="modal-body">
                    <h1>Register</h1>
                    {% from "includes/_formhelpers.html" import render_field %}
                    <form method="POST" action="">
                      <div class="form-group">
                        {{render_field(form.name, class_="form-control")}}
                      </div>
                      <div class="form-group">
                        {{render_field(form.email, class_="form-control")}}
                      </div>
                      <div class="form-group">
File "C:\ProgramData\CooperConda\lib\site-packages\jinja2\environment.py", line 430, in getattr
return getattr(obj, attribute)
jinja2.exceptions.UndefinedError: 'form' is undefined
The debugger caught an exception in your WSGI application. You can now look at the traceback which led to the error.
To switch between the interactive traceback and the plaintext one, you can click on the "Traceback" headline. From the text traceback you can also create a paste of it. For code execution mouse-over the frame you want to debug and click on the console icon on the right side.

You can execute arbitrary Python code in the stack frames and there are some extra helpers available for introspection:

dump() shows all variables in the frame
dump(obj) dumps all that's known about the object
Brought to you by DON'T PANIC, your friendly Werkzeug powered traceback interpreter.

jinja2.exceptions.UndefinedError
jinja2.exceptions.UndefinedError:“表单”未定义
回溯（最近一次呼叫最后一次）
文件“C:\ProgramData\CooperConda\lib\site packages\flask\app.py”，第2463行，在调用中__
返回self.wsgi_应用程序（环境，启动响应）
文件“C:\ProgramData\CooperConda\lib\site packages\flask\app.py”，第2449行，在wsgi_应用程序中
response=self.handle\u异常（e）
文件“C:\ProgramData\CooperConda\lib\site packages\flask\app.py”，第1866行，在句柄中
重放（exc_类型、exc_值、tb）
文件“C:\ProgramData\CooperConda\lib\site packages\flask\\u compat.py”，第39行，重新登录
增值
wsgi_应用程序中的文件“C:\ProgramData\CooperConda\lib\site packages\flask\app.py”，第2446行
response=self.full\u dispatch\u request（）
文件“C:\ProgramData\CooperConda\lib\site packages\flask\app.py”，第1951行，完整发送请求
rv=自身处理用户异常（e）
文件“C:\ProgramData\CooperConda\lib\site packages\flask\app.py”，第1820行，在handle\u user\u异常中
重放（exc_类型、exc_值、tb）
文件“C:\ProgramData\CooperConda\lib\site packages\flask\\u compat.py”，第39行，重新登录
增值
文件“C:\ProgramData\CooperConda\lib\site packages\flask\app.py”，第1949行，完整发送请求
rv=自我分派请求（）
文件“C:\ProgramData\CooperConda\lib\site packages\flask\app.py”，第1935行，在调度请求中
返回self.view_函数[rule.endpoint]（**req.view_参数）
文件“C:\Users\tlquickl\devel\MyFlaskApp\app.py”，第61行，
 # Get stored hash
            data = result.fetchone()
            if data is None:
                error = 'Username not found'
                return render_template('home.html', error=error, ***form=form***)
            password = data['Password']
            # Compare Passwords
            if sha256_crypt.verify(password_candidate, password):
                # Passed
                session['logged_in'] = True
                session['username'] = username
                flash('You are now logged in', 'success')
                return redirect(url_for('dashboard'))
            else:
                error = 'Invalid login'
            return render_template('home.html', error=error, ***form=form***)
    return render_template('home.html', form=form)