CODEWITHSUNDEEP
pythonflaskwsgi
JoshieSimmons
JoshieSimmons

Reputation: 2791

What are Flask Blueprints, exactly?

I have read the official Flask documentation on Blueprints and even one or two blog posts on using them.

I've even used them in my web app, but I don't completely understand what they are or how they fit into my app as a whole. How is it similar to an instance of my app but not quite? The documentation is comprehensive but I seek a layman explanation or an enlightening analogy to spark it for me. I was sufficiently perplexed when a colleague asked me to explain a Flask blueprint to them that I elected to ask here.

Upvotes: 231

Views: 96269

Answers (6)

Tran Cuong
Tran Cuong

Reputation: 527

As pointed out in a comment by @Devasish, this article provides a good answer:

http://exploreflask.com/en/latest/blueprints.html
[Edit: The above URL is dead, but you can see it on archive.org]

Quoting from the article:

An example of this would be Facebook. If Facebook used Flask, it might have blueprints for the static pages (i.e. signed-out home, register, about, etc.), the dashboard (i.e. the news feed), profiles (/robert/about and /robert/photos), settings (/settings/security and /settings/privacy) and many more. These components all share a general layout and styles, but each has its own layout as well

This is a very good interpretation, especially the part "if Facebook used Flask". It gives us a concrete situation to visualize how Blueprint actually works.

Upvotes: 13

Kraken
Kraken

Reputation: 5890

Coming from the Express.js world, I think it parallels well with Express.Router Middleware, with the added benefit that it facilitates the organization and route decoration for you. It's scaffolding for the middleware and middleware rolled into one.

Upvotes: 0

LFMekz
LFMekz

Reputation: 723

I too just stumbled up this myself and was confused after reading a few of the documentation sources. At first I thought it was like C#/Java OOP Interface Implementation style where you define some stuff but dont have to worry about it implementation details til later. However, I stumbled up this page which puts it in very very laymens (and quite hilarious present-day events) terms. https://hackersandslackers.com/flask-blueprints/

Essentially one benefit that is mentioned in the link and provides me a clear idea of it's real world usage is that I can effectively logically organize/divide the app into several parts that only need to be concerned with it's own affairs. So it provides some designed encapsulation.

Edit: I'm currently using it to segment out my webapps code. It was good decision too because I found the lead designer wants to make the frontend in Vue.js. Which I havent used yet but looking at it's project files would look far more messy and probably provide many naming collision prone instances due to files with similar names

Upvotes: 9

Henshal B
Henshal B

Reputation: 2002

For bigger projects, all your code shouldn't be in the same file. Instead you can segment or split bigger codes into separate files, mostly based on functionality. Like bricks forming a wall.

A simple Flask app

app = Flask(__name__)

A blueprinted Flask app

import from_any_module.part_1
import from_other_module.part_2

app = Flask(__name__)

app.register_blueprint(part_1)
app.register_blueprint(part_2)

A blueprint in the above app

from flask import Blueprint
part_1 = Blueprint(part_1)

@part_1.route('/url')
def function()
    return view

Upvotes: 12

Ssali Jonathan
Ssali Jonathan

Reputation: 107

A Flask blueprint helps you to create reusable instances of your application. It does so by organizing your project in modules. Those modules are then registered the main application. They help in creating an application factory.

Upvotes: 4

Sean Vieira
Sean Vieira

Reputation: 160033

A blueprint is a template for generating a "section" of a web application. You can think of it as a mold:

A medallion mold with a gold medallion freshly removed from it

You can take the blueprint and apply it to your application in several places. Each time you apply it the blueprint will create a new version of its structure in the plaster of your application.

# An example
from flask import Blueprint

tree_mold = Blueprint("mold", __name__)

@tree_mold.route("/leaves")
def leaves():
    return "This tree has leaves"

@tree_mold.route("/roots")
def roots():
    return "And roots as well"

@tree_mold.route("/rings")
@tree_mold.route("/rings/<int:year>")
def rings(year=None):
    return "Looking at the rings for {year}".format(year=year)

This is a simple mold for working with trees - it says that any application that deals with trees should provide access to its leaves, its roots, and its rings (by year). By itself, it is a hollow shell - it cannot route, it cannot respond, until it is impressed upon an application:

from tree_workshop import tree_mold

app.register_blueprint(tree_mold, url_prefix="/oak")
app.register_blueprint(tree_mold, url_prefix="/fir")
app.register_blueprint(tree_mold, url_prefix="/ash")

Once it is created it may be "impressed" on the application by using the register_blueprint function - this "impresses" the mold of the blueprint on the application at the locations specified by url_prefix.

Upvotes: 339

Related Questions