A presentation -- prepared for the RoPython #1 workshop -- about general aspects regarding REST (REpresentational State Transfer) as a paradigm for developing Web services, plus several Python solutions and examples.

1. Dr. Sabin Buraga – www.purl.org/net/busaco
Python “sinners” must
R⚗ST

2. warning:
some sensitive people might consider
this presentation somewhat offensive
in this situation, these persons are advised
to immediately abandon all humour
and better visit gore Websites for the real-life “fun”
Thank you for understanding!
100% pure sarcasm & irony included

3. So, our Web application
must provide certain
functionalities* to be
consumed by software
(not only by humans)…
* desired data requested via HTTP
http://www.boredpanda.com/funny-chinese-translation-fails/

4. …Oh, by the way,
what the Web is?


5. …Oh, by the way,
what the Web is?
content ≅ sexy <mark-ups/>
+ stylish CSS heartaches
http://www.funnypicss.com/humor/i-know-html/

6. …Oh, by the way,
what the Web is?
interaction ≅ URI + hypermedia
(HTTP delights?)
http://httpstatusdogs.com/

7. …Oh, by the way,
what the Web is?
development ≅ client and/or
server-side programming %#^&!
paradigms/languages/frameworks/magic/…
http://stressandanger.wordpress.com/funny-pictures/

8. In order to satisfy some 〠 needs,
the software must offer certain ☠ services*
http://brog.engrish.com/
* the action of helping or doing work for someone

9. Web service
a piece of s…oftware providing a s…pecific functionality
http://wallpaperstop.co/wallpapers/2013/07/Cats-Funny-Meme-272x480.jpg

10. Web service
a piece of s…oftware providing a s…pecific functionality
access to resources of (dis)interest – Instagram, Pinterest, Tumblr
boring news aggregators – Digg, Reddit
(“surreal”) maps – Bing Maps, Google Maps, Nokia HERE
instant mess(ages) – Jabber, Twitter, Twilio
world-wide stupidity – see Facebook (Open Graph Protocol)
(unsecure) data storage – Amazon S3, Dropbox, OneDrive
…and many, many, many others

11. Web service
developed & deployed by using W3C standards
URI (Unicorn Ridiculous Identifier) – aka Web address
access via HTTP (Hyper Trickiest Triviality Provider)
data formats:
JSON (JavaScript Orgiastic Needs)
XML (Exquisite Manual Labor)
…

12. Web service
a classical implementation:
using certain Web application servers/frameworks
for Python, some popular choices are
Django, Grok, TurboGears, web2py, Zope
https://wiki.python.org/moin/WebFrameworks

13. generic architecture of a traditional Web application
(N-tier application)
Client Web application Storage
(user interface) server/framework (data persistence)
Internet
(Web)

14. Web service
goal: processing the answer (data) provided by a given Web
site/application in order to (re)use it in our (client) programs
http://nedhardy.com/2013/04/22/17-hilarious-ad-placement-fails/

15. Web service
a naïve solution:
Web scraping
extracting data of interest
by parsing (incorrect)
HTML constructs
www.winhdwallpapers.com/funny/funny-html-code-hd-wallpaper-1080p

16. Web service
Web scraping
several Python libraries:
Beautiful Soup – www.crummy.com/software/BeautifulSoup/
html5lib-python – https://github.com/html5lib/html5lib-python
lxml – http://lxml.de/
Scrappy – http://scrapy.org/

17. How about an interesting*
paradigm of Web service
development?
* aka pragmatic
http://commons.wikimedia.org/wiki/File:France_Paris_Notre-Dame-Adam_and_Eve.jpg

18. REST (REpresentational State Transfer)
Web development focused on
the representation(s) of a resource
Roy Fielding – PhD Thesis (2000)

19. REST (REpresentational State Transfer)
Web development focused on
the representation(s) of a resource
e.g., user, blog, article,
photo, source-code,…

20. REST (REpresentational State Transfer)
Web development focused on
the representation(s) of a resource
HTML, PNG, SVG, JSON,…

21. REST (REpresentational State Transfer)
Web development focused on
the representation(s) of a resource
denoted by MIME types:
text/html, application/json,…

22. each resource can have multiple representations
accessed via HTTP requests

23. clients (browsers, robots, players,…) interact
with the resource representations via HTTP verbs:
create: POST, retrieve: GET, update: PUT, delete: DELETE
representation2
(Atom)
resource
URI
URLURL
GET POST GET DELETE
representation1
(HTML)

24. resource1
representation1
(HTML)
http://blog.info/
http://blog.info/post
http://blog.info/post/edit
http://blog.info/news
GET
resource2
resource3
resource4
GET
POST
representation2
(HTML) representation3
(HTML)
representation4
(Atom)

25. resource1
representation1
(HTML)
http://blog.info/
http://blog.info/post
http://blog.info/post/edit
http://blog.info/news
GET
resource2
resource3
resource4
GET
POST
representation2
(HTML) representation3
(HTML)
representation4
(Atom)
HATEOAS (Hypermedia As The Engine Of Application State)

26. So, some practical
advises about building
RESTful Web services?
http://www.funpedia.net/imgs/may11/very-funny-signs-06.jpg

27. Use nouns for each class of resources
to be managed by your service
User
Document – alternatives: Photo, Product, Software
Metadata – e.g., Comment, Format, Platform, Tag,…

28. Use nouns for each class of resources
to be managed by your service
collections of “things” (typically, plural)
/snakes
unique identifiers for every member of a collection
/snakes/python versus /snakes/69

29. SoundCloud API
types of resources:
tracks, users, current user (me),
playlists, groups, comments
http://developers.soundcloud.com/

30. Name each resource by using URLs
http://www.slideshare.net/busaco/presentations
http://www.imdb.com/title/tt0401383/
http://www.last.fm/music/Moby
http://vimeo.com/channels/731014

31. Design accepted representations to be sent by
potential clients
+
optional parameters
(useful for pagination, partial responses, filtering,…)
/snakes?limit=3&offset=14
/snakes?fields=name,age,description

32. Choose the representation(s) of the response
to be sent to client
consider existing standardized data formats
e.g., HTML, Atom, JSON,…
Accept: application/json (Digg)
/venue.json (Foursquare)
http://api.sciencemuseum.org.uk/exhibitions/?output=json

33. interactive access to the data provided by a public Web service
http://developer.nytimes.com/
JSON response

34. Integrate resources via URLs + Web forms

35. Create use cases
specify exception/error conditions
via HTTP status codes + additional information
200 OK, 303 See Other, 400 Bad Request, 404 Not Found,…
http://httpstatus.es/

36. “Never release an API without a version
and make the version mandatory.”—Brian Mulloy (2012)
http://feeds.delicious.com/v2/{format}/{username}
?v=1.0 (Facebook)

37. Some (programming)
tools for developers?
http://www.weirdasianews.com/category/engrish/

38. Python HTTP clients
classical built-in modules:
httplib (Python 2)
http.client (Python 3)

39. Python HTTP clients
a specific library:
Unirest for Python – http://unirest.io/python.html

40. Developing RESTful Web services in Python
one of our favorite frameworks:
Bottle, CheeryPy, Django REST, Flask, web.py

41. using a Python wrapper for
a specific Web service/API:
www.pythonapi.com

42. Useful Web resources
for learning & making
experiments?

43. building a REST service:
Learn REST: A RESTful Tutorial
www.restapitutorial.com
Thoughts on RESTful API Design
https://restful-api-design.readthedocs.org
Implementing REST
https://code.google.com/p/implementing-rest/

44. testing our/others APIs:
Make HTTP Requests
http://www.hurl.it/
HTTP Request & Response
http://httpbin.org/
Apigee Console
https://apigee.com/console/

45. don’t forget to consult:
ProgrammableWeb
http://www.programmableweb.com/
The Web engineer’s online toolbox
ivanzuzak.info/2012/11/18/the-web-engineers-online-toolbox.html

46. R⚗ST
(and some Python)
http://photos1.blogger.com/blogger/3043/2944/1600/woman-snake-1280.jpg