How to Create Blueprint in Flask: Simple Guide

In Flask, create a Blueprint by importing it from flask, defining it with a name and import name, then registering it on your main app with app.register_blueprint(). Blueprints help organize routes and views into reusable modules.

Syntax

A Blueprint is created by calling Blueprint(name, import_name). Then you define routes on it like a normal Flask app. Finally, register it on the main app with app.register_blueprint(blueprint).

• name: a string identifier for the blueprint
• import_name: usually __name__, helps Flask locate resources

python

from flask import Blueprint

bp = Blueprint('bp_name', __name__)

@bp.route('/')
def home():
    return 'Hello from Blueprint!'

# In main app:
# app.register_blueprint(bp)

Example

This example shows how to create a blueprint, define a route on it, and register it with the main Flask app. When you visit /bp/, it returns a message from the blueprint.

python

from flask import Flask, Blueprint

bp = Blueprint('bp', __name__, url_prefix='/bp')

@bp.route('/')
def bp_home():
    return 'Hello from Blueprint!'

app = Flask(__name__)
app.register_blueprint(bp)

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

Output

Running the app and visiting http://localhost:5000/bp/ shows: Hello from Blueprint!

Common Pitfalls

• Forgetting to register the blueprint on the main app means routes won’t work.
• Not setting url_prefix can cause route conflicts.
• Using the wrong import_name can cause resource loading errors.
• Defining routes outside the blueprint or app context causes errors.

python

from flask import Flask, Blueprint

# Wrong: Not registering blueprint
bp = Blueprint('bp', __name__)

@bp.route('/')
def home():
    return 'Hello'

app = Flask(__name__)
# Missing: app.register_blueprint(bp)  # This causes routes to not work

# Correct way:
# app.register_blueprint(bp)

Quick Reference

Blueprint Usage Step	Description
Import Blueprint	from flask import Blueprint
Create Blueprint	bp = Blueprint('name', __name__, url_prefix='/prefix')
Define Routes	@bp.route('/') def func(): return 'response'
Create Flask App	app = Flask(__name__)
Register Blueprint	app.register_blueprint(bp)
Run App	app.run(debug=True)

Key Takeaways

Create a Blueprint with Blueprint('name', __name__, url_prefix='/prefix') to organize routes.

Define routes on the blueprint just like on the main Flask app.

Always register the blueprint on the main app using app.register_blueprint().

Use url_prefix to avoid route conflicts and group blueprint routes.

Blueprints help keep your Flask app modular and easier to maintain.