title: What does it mean to register a blueprint into the app in Flask?
body: <p>I am going through the flask documentation and the source code of flask to develop a deeper understanding of the framework. Also, I have gone through <a href="https://stackoverflow.com/questions/24420857/what-are-flask-blueprints-exactly">What are Flask Blueprints, exactly?</a>.
  I understand how blueprint helps in modularization of code and reuse of functions.</p>
  
  <p>But it seems that I am not grokking Flask app object and what does it mean to register a blueprint to it.</p>
  
  <p>In the code documentation, it says that <code>a blueprint defers the need for an application by recording them for later registrations</code>. Also, <code>a Blueprint is an object that allows defining application functions without requiring application object ahead of time.</code></p>
  
  <p>I understand that we use blueprint the same way. As in instead of @app.route, you use, @bp.route and then register that bp into the app by calling <code>app.register_blueprint(some_bp)</code>.</p>
  
  <p>Can somebody help me understand it in a better way and help fill the gap in my understanding?</p>