{% extends "bootstrap/base.html" %}
{% block title %} {{ title }} {% endblock %}
{% block navbar %}
<nav class="navbar navbar-expand-lg navbar-dark bg-dark">
    <div class="container">
        <a href="/" class="navbar-brand">Home</a>
        <div class="collapse navbar-collapse">
            <ul class="navbar-nav">
                <li class="nav-item">
                    <a href="#" class="nav-link">Menu 1</a>
                </li>
                 <li class="nav-item">
                    <a href="#" class="nav-link">Menu 2</a>
                </li>
            </ul>
        </div>
    </div>
</nav>
{% endblock %}
{% block content %}
<div class="container">
        <h2>Witaj Flask!!!</h2>
    {% if name %}
        <h2>Witaj, {{ name }}</h2>
    {% else %}
        <h2>Witaj, nieznajomy</h2>
    {% endif %}
</div>
{% endblock %}


from flask import Flask, render_template
from flask_bs4 import Bootstrap

app = Flask(__name__)
bootstrap = Bootstrap(app)

@app.route('/')
def index ():
    return render_template('index.html', title='Strona główna')

@app.route('/user/<name>')
def user(name):
    return render_template('index.html',
                            title = 'Strona glowna', name=name)

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