pip install Flask-Bootstrap Flask-Nav

from flask import Flask, flash
from flask_bootstrap import Bootstrap
from flask_nav import Nav
from flask_nav.elements import Navbar, View, Subgroup

app = Flask(__name__)
app.config['SECRET_KEY'] = 'your_secret_key'  # 必须设置一个密钥

bootstrap = Bootstrap(app)
nav = Nav(app)

@nav.navigation()
def mynavbar():
    return Navbar(
        'My App',
        View('Home', 'index'),
        Subgroup('Settings',
            View('Profile', 'profile'),
            View('Logout', 'logout')
        )
    )

@app.route('/')
def index():
    flash('Welcome to our site!', 'success')
    return render_template('index.html')

@app.route('/profile')
def profile():
    flash('This is your profile page.', 'info')
    return render_template('profile.html')

@app.route('/logout')
def logout():
    flash('You have been logged out.', 'warning')
    return redirect(url_for('index'))

{% extends "bootstrap/base.html" %}

{% block content %}
    {{ nav.topbar() }}
    {% with messages = get_flashed_messages(with_categories=true) %}
        {% if messages %}
            {% for category, message in messages %}
                <div class="alert alert-{{ category }}">
                    {{ message }}
                </div>
            {% endfor %}
        {% endif %}
    {% endwith %}
    {% block page_content %}{% endblock %}
{% endblock %}

{% extends "base.html" %}

{% block page_content %}
    <h1>Welcome to the Home Page</h1>
    <!-- 其他内容 -->
{% endblock %}