Flask应用中/login路由页面无法显示的问题求助

问题概述 #

开发Flask应用时，配置了/login路由实现登录页面功能，但访问http://127.0.0.1:5000/login时登录页面无法正常显示。已创建login.html并继承自带有Bootstrap导航栏的base.html，主应用代码按教程编写但问题未解决。

代码展示 #

主应用文件 #

from flask import Flask, redirect, url_for, render_template, request
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)


@app.route("/")
def home():
    return render_template("index.html")

@app.route("/login", methods=["GET", "POST"])
def login():
    if request.method == "POST":
        user = request.form["nm"]
        return redirect(url_for("user", usr=user))
    else:
        return render_template("login.html")

@app.route("/<usr>")
def user(usr):
    return f"<h1>{usr}</h1>" 

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

login.html #

{% extends "base.html" %}
{% block title %}Login Page{% endblock %}

{% block content %}
<form action="#" method="post">
    <p>Name:</p>
    <p><input type="text" name="nm" /></p>
    <p><input type="submit" value="submit"/></p>
</form>
{% endblock %}

base.html #

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <link rel="stylesheet" href="{{ url_for('static', filename='css/main.css') }}">
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@4.3.1/dist/css/bootstrap.min.css" integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
    {% block head %}{% endblock %}
</head>
<body>
    <nav class="navbar navbar-expand-lg navbar-light bg-light">
        <a class="navbar-brand" href="#">FINANCEPAL</a>
        <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">
          <span class="navbar-toggler-icon"></span>
        </button>
        <div class="collapse navbar-collapse" id="navbarNavDropdown">
          <ul class="navbar-nav">
            <li class="nav-item active">
              <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#">Features</a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#">Pricing</a>
            </li>
            <li class="nav-item dropdown">
              <a class="nav-link dropdown-toggle" href="#" id="navbarDropdownMenuLink" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">
                Dropdown link
              </a>
              <div class="dropdown-menu" aria-labelledby="navbarDropdownMenuLink">
                <a class="dropdown-item" href="#">Action</a>
                <a class="dropdown-item" href="#">Another action</a>
                <a class="dropdown-item" href="#">Something else here</a>
              </div>
            </li>
          </ul>
        </div>
      </nav>
    {% block body %}{% endblock %}
    <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js" integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo" crossorigin="anonymous"></script>
    <script src="https://cdn.jsdelivr.net/npm/popper.js@1.14.7/dist/umd/popper.min.js" integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1" crossorigin="anonymous"></script>
    <script src="https://cdn.jsdelivr.net/npm/bootstrap@4.3.1/dist/js/bootstrap.min.js" integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM" crossorigin="anonymous"></script>
   
</body>

</html>

问题原因与解决方法 #

核心问题：模板块名称不匹配 #

base.html中定义的内容插入块是{% block body %}，但login.html中使用的是{% block content %}——这个块在父模板中不存在，导致登录表单无法被渲染到页面中。

修复方案（二选一即可） #

方案1：修改login.html的块名称

将login.html中的{% block content %}改为{% block body %}，修改后代码如下：

{% extends "base.html" %}
{% block title %}Login Page{% endblock %}

{% block body %}
<form action="{{ url_for('login') }}" method="post">
    <p>Name:</p>
    <p><input type="text" name="nm" /></p>
    <p><input type="submit" value="submit"/></p>
</form>
{% endblock %}

方案2：在base.html中添加content块

在base.html的<body>部分，新增{% block content %}{% endblock %}，比如：

<!-- 保留原有的body块，新增content块 -->
{% block body %}{% endblock %}
{% block content %}{% endblock %}

额外优化建议 #

• 将form的action属性从#改为{{ url_for('login') }}，确保表单准确提交到登录路由，避免跳转异常。
• 确认模板文件路径：login.html和base.html需放在Flask默认的templates文件夹中，且主应用文件与templates文件夹同级。
• 若static/css/main.css不存在，可暂时删除该链接，避免控制台出现404错误。

内容的提问来源于stack exchange，提问作者Z1latro