6. Blueprint

A Blueprint in Flask is a way to organize your application into smaller and reusable components. It allows you to group related routes, templates, static files, and other functionality into a cohesive module. This helps in managing large applications by keeping related code together and promoting modular design.

Example of Using Blueprints in Flask

Let's say you have an application that has an admin interface and a user interface. You can create separate blueprints for each.

Create a Blueprint for the Admin Interface

First, create a directory for your admin blueprint and add the necessary files.

Directory Structure:

/yourapp
  /admin
    __init__.py
    routes.py
  app.py

admin/init.py:

from flask import Blueprint

admin_bp = Blueprint('admin', __name__)

from . import routes

admin/routes.py:

from flask import render_template
from . import admin_bp

@admin_bp.route('/admin')
def admin_home():
    return render_template('admin_home.html')

Create a Blueprint for the User Interface

Similarly, create a directory for your user blueprint and add the necessary files.

Directory Structure:

/yourapp
  /user
    __init__.py
    routes.py
  app.py

user/init.py:

from flask import Blueprint

user_bp = Blueprint('user', __name__)

from . import routes

user/routes.py:

from flask import render_template
from . import user_bp

@user_bp.route('/user')
def user_home():
    return render_template('user_home.html')

Register Blueprints in Your Main Application

Now, register the blueprints in your main application file.

app.py:

from flask import Flask
from admin import admin_bp
from user import user_bp

app = Flask(__name__)

app.register_blueprint(admin_bp, url_prefix='/admin')
app.register_blueprint(user_bp, url_prefix='/user')

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

Templates

Create templates for the admin and user interfaces.

templates/admin_home.html:

<!doctype html>
<html>
<head>
    <title>Admin Home</title>
</head>
<body>
    <h1>Welcome to the Admin Dashboard</h1>
</body>
</html>

templates/user_home.html:

<!doctype html>
<html>
<head>
    <title>User Home</title>
</head>
<body>
    <h1>Welcome to the User Dashboard</h1>
</body>
</html>

Explanation

Blueprint Creation: We create blueprints in admin/__init__.py and user/__init__.py.
Route Definition: Routes are defined in admin/routes.py and user/routes.py.
Blueprint Registration: In app.py, we register the blueprints with specific URL prefixes (/admin and /user).
Templates: Separate templates for the admin and user interfaces.

By using blueprints, you can keep your code organized and maintainable, especially as your application grows in complexity.

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