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Flasky Goodness
Kenneth Reitz
(Or Why Django Sucks?)
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Hi.
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@kennethreitz
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No content
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Open Source
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Python-Guide.org
• Documented best practices.
• Guidebook for newcomers.
• Reference for seasoned veterans.
• Don’t panic & always carry a towel.
The Hitchhiker’s Guide to Python
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Requests
HTTP for Humans
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Httpbin.org
$ curl http://httpbin.org/get?test=1
{
"url": "http://httpbin.org/get",
"headers": {
"Content-Length": "",
"Connection": "keep-alive",
"Accept": "*/*",
"User-Agent": "curl/7.21.4 ...",
"Host": "httpbin.org",
"Content-Type": ""
},
"args": {
“test”: “1”
},
"origin": "67.163.102.42"
}
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Et Cetera
• Legit: Git Work ow for Humans
• Envoy: Subprocess for Humans
• Tablib: Tabular Data for Humans
• Clint: CLI App Toolkit
• Autoenv: Magic Shell Environments
• OSX-GCC-Installer: Provokes Lawyers
275+ More
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Open Source
All The Things!
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Build for Open Source
• Components become concise & decoupled.
• Concerns separate themselves.
• Best practices emerge (e.g. no creds in code).
• Documentation and tests become crucial.
• Code can be released at any time.
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Abstraction
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Let’s build something.
We’ll use Django, of course.
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Django Benefits
• Makes modular decisions for you.
• Makes security decisions for you.
• Excellent documentation available.
• Installable third-party Django apps.
• Tremendous resources & community.
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Django Handles Things
• Admin & Management Interface
• Database Schema & Migrations
• User Pro les and Authentication
• User Sessions and Cookies
• Internationalization
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Anything is possible*.
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Django Application
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Django Application
Tools & Utilities Web Process Worker Process
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Single Codebases are Great
• All the bene ts of the Django stack.
• Figure out architecture as you go.
• Shared modules keep you DRY.
• Make broad and sweeping changes quickly.
• Only need to deploy once.
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No content
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Django Application
Management Tools
Supporting Services
Tools & Utilities Web Process Worker Process
Scheduled Tasks
Deferred Tasks
API Service
CRUD Admin
Data Persistence
User Interface
Authentication
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Single Codebases are Evil!
• Components are tightly coupled.
• Broad tribal knowledge is required.
• Iterative change of components di cult.
• Technical debt has a tendency to spread.
• Forced to deploy everything at once.
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Anything is possible*.
* But it’ll often be a monolithic app.
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CONSTRAINTS
FOSTER
CREATIVITY
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Constraints are Good
• Text Editors vs IDEs
• Prime vs Zoom Lenses
• Mac OS X vs Desktop Linux
• Pen & Paper vs Digital Notes
• Monolithic Apps vs Services
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Keep ‘em Separated
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Data Persistence
Developers End Users
API Service Frontend
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Build for Open Source
• Components become concise & decoupled.
• Concerns separate themselves.
• Best practices emerge (e.g. no creds in code).
• Documentation and tests become crucial.
• Code can be released at any time.
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Build for Services
• Components become concise & decoupled.
• Concerns seperate themselves.
• Best practices emerge (e.g. ideal tools).
• Documentation and contracts become crucial.
• Services can be scaled separately at any time
• Dogfood is delicious.
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Composability
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No content
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End Users
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End Users
Developers
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End Users
API Service
Developers
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API Service
End Users
API Service
Developers
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API Service
End Users
API Service
Developers
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API Service
End Users
API Service
API Service
Developers
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API Service
End Users
API Service
API Service
Developers
( )
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API Service
End Users
API Service
API Service
Developers
( )
Data Persistence
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API Service
End Users
API Service
Internal
API Service
Developers
( )
Data Persistence
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API Service
End Users
API Service
Internal
API Service
Developers
( )
Data Persistence
Message Queue Workers
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Let’s try it out.
We’ll use Django, of course.
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Django: It Just Sits There™
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Two Basic Components
API Service & Frontend Client
API Service Frontend Client
Data Interface
Business Logic
Authentication
User Interface
State and Sessions
Public Face
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Django for API Services
• Signi cant boilerplate code for simple views.
• No need for templates, tags, etc.
• API libraries are buggy; could use some love.
• if request.method == 'POST'
(and nothing else)
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Django as API Consumer
• Keep in mind, database is handled by API.
• Makes modular decisions for you.
• Deals with the database for you.
• Installable third-party Django apps.
(and nothing else)
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Django as API Consumer
• Everything is tied to the ORM.
• Third-party Django apps do too.
• User model requires sessions; isn’t exible.
(and nothing else)
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What’s Left?
?
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Flask
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Enter, Flask.
• HTTP Web Framework based on Werkzeug.
• Excellent for building web services.
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Elegant & Simple
from flask import Flask
app = Flask(__name__)
@app.route("/")
def hello():
return "Hello World!"
if __name__ == "__main__":
app.run()
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Flask Familiarities
• WSGI Application Framework.
• Built-in Templating System (Jinja2).
• Active community, extensions for everything.
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Flask Philosphies
• Started as an April Fool’s joke.
• Very minimal; 800 lines of code.
• Heavily tested; 1500 lines of tests.
• Exhaustively documented; 200 pages of docs.
• Layered API; built on Werkzeug, WSGI.
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Flask Differences
• Explicit & passable app objects.
• Simple, elegant API. No boiler plate.
• BYOB: Bring Your Own Batteries.
• No built-in ORM or form validation.
• Context locals. Keeps things looking clean.
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Flask Improvements
• Fewer batteries == greater exibility.
• Jinja2 is an incredible template system.
• Everything harnesses actual references.
• Con guration is a simple dictionary.
• It’s hard to build monolithic applications.
• Response objects are WSGI applications.
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Flask Improvements
• Werkzueug debugger.
• No import-time side e ects.
• Signals system outside of ORM.
• Tests are simpler with real app objects.
• return (content, status)
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Popular Extensions
• Flask-SQLAlchemy: Database Mapper.
• Flask-Celery: Delayed Jobs.
• Flask-Script: Management Commands.
• Flask-WTF: Form Validation.
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Shameless Plug
• Flask-SSLify: App HSTS (SSL) Policies
• Flask-GoogleFed: Google Federated Auth
• Flask-Heroku: Env Variable Con gurations
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Flask is a sharp tool for building
sharp services.
Use the right tool for the job.
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Torn?
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Flask vs.Django
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Alcohol
vs.
Ponies
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Why not both?
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Services are agnostic.
Just speak HTTP.
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github.com/kennethreitz
Questions?