Django Workshop at PythonPH Meetup (June 2013)

Download companion files here: http://github.com/jondanao/Surf-Magazine-Template

Many thanks to the Django community especially @pydanny and @audreyr who wrote Two Scoops of Django book. https://django.2scoops.org

https://twitter.com/jondanao
https://github.com/jondanao
http://danao.org/

Transcript

2. Jon Danao
3. Who is Jon Danao? • 30-something jack-of-all-trades developer • Head of Development for Digital Brand Management @ ABS-CBN • Ex Rock Star • Award Winner (CMMA - Best Website 2001) • Award Winner (Yahoo! Open Hack Day - Best Social Hack 2009)
4. Who is Jon Danao? • Speak several languages: English, Filipino, Cebuano, Chavacano, HTML, ActionScript, Java, PHP, SQL, Lua, Javascript, Objective-C and Python • Run a blog at danao.org • Run another blog at silkroutes.com • Email me at jondanao@gmail.com
5. Who are you? • Students? • Teachers? • Professional Developers? • Managers? • C/C++? • PHP / ASP.NET / Ruby / Java? • PYTHON???
6. Outline 1. Introduction 2. The Project 3. Dev Machine 4. Flow 5. Dive into Django
7. Introduction
8. What is Django? • Shiny Python web framework • Encourages RAD and clean design • Enforces MVC • Focuses on automation and DRY • Like Ruby on Rails, Code Igniter (PHP), ASP.NET MVC
9. Why do I Django? —
10. Philosophies
11. Philosophies • Loose coupling = Flexibility • KISS = Clarity • RAD = Agility • DRY = Reusability • Consistency = Predictability • “For perfectionists with deadlines”
12. Who uses Django?
13. Who uses Django? • All Mozilla sites are now built with Django • Firefox add-ons site: - 150M views/month - 500M API hits/day
14. Who uses Django? • 25k requests/sec • 700k websites • 20M page views/day • 30M profiles • 170M comments • 500M unique visitors
15. Who uses Django? • 3M users • 18M visitors/month • 80M objects in S3 • 500M pins • 2.5B page views/month • 1.6B follower rows
16. Who uses Django? • 90M monthly active users • 40M photo uploads/day • 8500 likes/second • 1000 comments/second • 1B push notifications • $1B
18. The Surf Magazine Project
19. UI Design
20. URL Design website.com/ website.com/category/ website.com/category/id/article-slug/ website.com/api/category.json website.com/api/category/id.json
21. URL Examples website.com/ website.com/sports/ website.com/sports/123/ufc-champion/ website.com/api/sports.json website.com/api/sports/123.json
22. URL Design
23. Dev Machine 1. Python http://www.python.org/getit 2.Pip sudo easy_install pip 3.VirtualEnv sudo pip install virtualenv 4. Git http://git-scm.com/downloads 5. SQLite Manager (optional)
24. Flow Concept Walkthrough Hands-on
25. Code of Conduct • Be welcoming, friendly and patient • Be considerate • Be respectful • Be careful in the words that you choose • Be constructive than destructive speakup.io/coc.html & djangoproject.com/conduct
26. Dive into Django
27. Pip • Python CLI package management system • Easy to install a package $ pip install package-name • Easy to uninstall a package $ pip uninstall package-name • Easy to list all installed packages $ pip freeze > requirements.txt • Easy to install package list $ pip install -r requirements.txt
28. Git • DVCS or SCM • Developed by Linus Torvalds • Fast, simple, non-linear, work offline • Practice: http://www.atlassian.com/git/ $ git init $ git status $ git add $ git commit
29. VirtualEnv • Creates isolated Python environments • Dependencies between projects don’t mix • Like having multiple XAMPP installations
30. VirtualEnv python.ph pycon.ph python 2.7 python 3.3 django 1.4 django 1.5 mysql-python 1.2.3 pymysql 0.5 (python-env) (pycon-env)
31. Walkthrough 1
32. Project • Project is a collection of apps and site configurations • Can be created via command line • Auto-generates some code - init, settings, urls, wsgi
33. Walkthrough 2
34. Database • No point of using Django if site is static • Support for PostgreSQL, SQLite3, MySQL, Oracle • GIS works really well with PostgreSQL
35. Walkthrough 3
36. Project Structure website.com !"" apps !"" db !"" media !"" project # !"" __init__.py # !"" settings.py # !"" urls.py # $"" wsgi.py !"" static !"" templates !"" venv !"" .gitignore !"" manage.py !"" README.md $"" requirements.txt
37. Settings • Handling file paths is difficult • Root of your machine != root of server • Hardcoding paths is bad • Configure all necessary options
38. Walkthrough 4
39. Best Practice Always pip freeze after installing new packages
40. Admin Site • Automatic creation of admin interfaces for models • Pseudo CMS for CRUD operations • Models can opt to hook into the admin site
41. Philosophy Writing admin interfaces is boring and repetitive.
42. Walkthrough 5
43. Best Practice Always syncdb after activating new apps
44. MVC
45. Model • Class that represents objects in db • Defines structure of data • Class = Table / Property = Column • Talks to the ORM that talks to the db • ORM eliminates writing of SQL
46. Example • Article as our model • It has properties like title, category, author, content, tags, published date • This will be translated into a db table
47. Philosophy Explicit is better than implicit.
48. Template • Renders HTML • Uses custom pseudo programming syntax • Very designer friendly
49. Philosophies Discourage redundancy. Be decoupled from HTML. XML should not be used a template language.
50. View • Handles request passed on via the URLConf • Gets data from the model and hands them over to the template for rendering • Determines WHAT data the user should see, not HOW data should be rendered
51. Philosophies Simplicity. Loose coupling.
52. App • Small library designed to represent a single aspect of a project (module/package/app) • A piece of functionality like articles, comments, ratings, products, polls, events • App = Django / Module = Python • A project can have multiple apps. An app can be in multiple projects. • In Python, to convert a folder into module, just add __init__.py
53. Philosophies Write programs that do one thing and do it well. If an app can’t be explained in a single sentence, it should be broken up. Should be reusable, pluggable, distributable.
54. Walkthrough 6
55. Best Practices Your app’s name should be the plural version of its main model Keep apps small, maximum of 5 models
56. Admin.py • Create admin.py inside app folder if you want to your models to appear in admin site • Register the models you want to be editable
57. Walkthrough 7
58. Django Flow
59. Django Flow Client URL View Model Tpl 1 Client requests a page via a URL 1 2 Django checks URLConf for URL patterns and executes view function to handle request 2 3 View requests data from model 3 4 Model queries the database and returns data to the view 4 5 View passes the data to template 5 6 Template renders data and returns HTML to the view 6 7 View returns HTML to the browser 7
60. URLConf • Hooks a particular URL pattern to a view function • Uses regex for maximum flexibility • Table of contents for site or app urlpatterns = patterns('', url(r'^articles/(\d{4})/$', 'news.views.year_archive'), url(r'^articles/(\d{4})/(\d{2})/$', 'news.views.month_archive'), url(r'^articles/(\d{4})/(\d{2})/(\d+)/$', 'news.views.article_detail'), )
61. Philosophies Loose coupling. Infinite flexibility. Definite URLs.
62. Walkthrough 8
63. Querying the Model • Retrieve all objects (aka SELECT *) all_articles = Article.objects.all() • Retrieve specific objects with filters (aka WHERE clause) draft_articles = Article.objects.filter(status=1) published_articles = Article.objects.exclude(status=1) • Chaining filters (aka AND operator in where) latest_paquiao_articles = Article.objects. filter(status=1). exclude(title=‘Manny Villar Wins!’)
64. Querying the Model • Limiting and offsetting results articles = Article.objects.all()[:5] articles = Article.objects.all()[5:10] • Sorting objects articles = Article.objects.all().order_by(‘title’) articles = Article.objects.all().order_by(‘-title’) • Retrieving single object article = Article.objects.get(id=1)
65. Dunder Methods • __init__, __file__, __unicode__ • Pythonic, common and idiomatic methods • Used as field lookups in filter() , exclude() , get() • Extremely powerful and intuitive
66. Field Lookups • Basic model lookups syntax: field__lookuptype = value Article.objects.filter(title__exact=‘Django is my Pony’) Article.objects.filter(title=‘Django is my Pony’) Article.objects.filter(title__contains=‘Python’) Article.objects.filter(title__startswith=‘Django’) Article.objects.filter(pub_date__gte=‘2013-02-01’) • Model relationship lookups syntax: field__foreignfield__lookuptype = value Article.objects.filter(category__slug__contains=‘global’)
67. Walkthrough 9
68. Template Engine • Renders HTML, CSV, JSON, XML... any text format, just specify content-type • Uses basic programming constructs • Call function or do logic: {% ... %} • Print variable: {{ foo }} • Filters: {{ foo|bar }}
69. Walkthrough 10
70. Template Engine • {% load %} - loads custom template tag • {% block %} - defines a block that can be overridden by child templates. Blocks are placeholders • {% extends %} - inherits from a parent or base template aka Template Inheritance • includes vs extends: • extends is the “inside-out” version of server-side includes • includes: define sections that are common • extends: define sections that are unique
71. Includes: define sections that are common Header Footer Extends: define sections that are unique Content Header Footer Content
72. Walkthrough 11
73. Recap • What is Django? • What is MTV? • What is Loose Coupling? • What is KISS? • What is RAD? • What is DRY?
74. Recap • What is the advantage of using VirtualEnv? • After installing a new package, what do you do next? • What is an app? • How do you create a Python module? • After activating new apps in settings, what do you do next?
75. Recap • What is the Admin site? • What do you do if you want your models to appear in the Admin site? • Write a query that gets 5 articles by a certain author and sort them alphabetically. • What is the use of dunder methods in queries? • What is template inheritance?
76. Maraming Salamat!
77. Bonus: Deploy to Heroku • Heroku is PaaS on top of AWS (IaaS) • Installs necessary dependencies by reading the requirements.txt • In Procfile we declare our manage.py runserver command • Easy deployment using git push!
78. Walkthrough 12