Django 101

DJANGO 101 LES MINES - NANCY Boris Feld - 28/09/2016

ABOUT ME • Python Dev / sqreen.io • DevOps •
! lothiraldan • [email protected]

PRINCIPLES

GOODWILL PRINCIPLE • Everyone did its best in the the
limits of their knowledge and ability at a certain time • Everyone has a life outside this classroom but will do his best for this not to interfere with the class. • Every assessment has a goal: identifying room for improvement.

BEFORE ALL http://www.commitstrip.com/ fr/2016/09/09/the-mistakes- of-youth/

EVERYONE IS HERE TO LEARN SOMETHING TODAY

- Boris FELD « Code is a side-product of application. 
Communication skills are much more valuable than coding one. »

FORMAT • https://docs.djangoproject.com/fr/1.10/intro/ • Github project • At least a
commit at each part

GIT TIP • Use https://gist.github.com/Lothiraldan/ 0dcac9ad04752ba39ab15300ef4da3d6 for .gitignore

WEB FRAMEWORK • Web Frameworks are a toolset designed to
support the development of web applications. • Web Frameworks usually provides functions for common tasks like database access, HTML templating or session management. • They speed the development of web applications by taking care of common tasks.

DJANGO • Most popular Python web framework. • First version
in July 2005. • The framework was named after guitarist Django Reinhardt.

DJANGO TUTORIAL https://docs.djangoproject.com/fr/1.10/intro/tutorial01/

CONCEPT HTTP REQUEST GET / HTTP/1.1 Host: 127.0.0.1:8000 Connection: keep-alive
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36 Hello: Nancy

PROCESSING HTTP

DJANGO PROCESSING

CONCEPT HTTP RESPONSE HTTP/1.0 200 OK Date: Sun, 25 Sep
2016 10:58:40 GMT Server: WSGIServer/0.1 Python/2.7.12 X-Frame-Options: SAMEORIGIN Content-Type: text/html <!DOCTYPE html> <html lang="en"><head> 1. Version de HTTP 2. Status code (200 OK) 3. Headers 4. Body

200 OK

CONCEPT STATUS CODE • Indicates the presence of errors or
validity of a response. • https://en.wikipedia.org/wiki/ List_of_HTTP_status_codes • https://http.cat/ • https://httpstatusdogs.com/

DJANGO TUTORIAL https://docs.djangoproject.com/fr/1.10/intro/tutorial02/ Don’t touch the DATABASE in settings.py ﬁle

CONCEPT ORM • Object Relational Mapping is a technique to
access relational data through object-oriented code. • It abstract part of the relational complexity required to access data.

CONCEPT ORM • Instead of doing: • You can do:
cursor = connection.Cursor() cursor.query('SELECT "polls_question"."id", "polls_question"."question_text", "polls_question"."pub_date" FROM "polls_question" WHERE "polls_question"."id" = ?', 1) result = cursor.fetchone() q = Question.objects.get(pk=1)

CONCEPT ADMIN INTERFACE • While website often a presentation of
the data for the customers (front-end), we generally need one for administrating the website, like resetting a password for an user. • Django comes up with an almost free admin, so enjoy!

DJANGO TUTORIAL https://docs.djangoproject.com/fr/1.10/intro/tutorial03/ Challenge: Create a poll from the CLI
and display it.

CONCEPT TEMPLATING Separation of concerns between data retrieval, request dispatching
and presentation.

CONCEPT MVC

CONCEPT MODEL • Responsible for accessing the data • Expose
a nice and friendly way to do so

CONCEPT CONTROLLER • Process the HTTP Request • Call the
model for getting data • Choose an acceptable view

CONCEPT VIEW • Format the data for the user in
one format • It’s usually an HTML page

- CONCEPT Unix Philosophy « Do One Thing and Do
It Well »

CONCEPT SEPARATION OF CONCERNS • Why separating the responsibilities? •
Easier to maintain • Easier to replace

WHAT BENEFITS? • For the model ? • For the
view ? • For the controller ?

WHAT BENEFITS? • For the model ? • Other sources
of data (ﬁle system, nosql, cache, …) • For the view ? • Other formats of presentation (json, xml, cvs, …) • For the controller ? • Can be left untouched when other parts change.

DJANGO TUTORIAL https://docs.djangoproject.com/fr/1.10/intro/tutorial04/ Challenge: Write custom ListView and DetailView.

ACCESS HTTP REQUEST POST /polls/1/vote/?foo=bar HTTP/1.1 Host: 127.0.0.1:8000 Connection: keep-alive
csrfmiddlewaretoken=…&choice=2 path method GET POST

CONCEPT CRUD • Most applications behavior can be simpliﬁed to:
• Create • Read • Update • Delete

CONCEPT BUSINESS LOGIC • Most website value reside in their
business logic and capabilities to make actions. • Basic CRUD actions are much less valuable but shouldn’t be overlooked, better let Django handle these situations for you. • You better wrote less code but more valuable code.

DJANGO TUTORIAL Skip https://docs.djangoproject.com/fr/1.10/intro/tutorial05/ But read it one day!

DJANGO TUTORIAL https://docs.djangoproject.com/fr/1.10/intro/tutorial06/

Django 101

Django 101

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