Introduction to Django

Django and Heroku

Transcript

1. Introduction to Django Kien Nguyen Trung
2. Kien Nguyen Trung github.com/kiennt kiennt.com
3. What is django
4. Django is high-level Python Web framework that encourages rapid development and clean, pragmatics design.
5. Philosophy Rapid Development Loosely coupled Reusable Applications Dont Repeat Yourself (DRY)
6. Django sites instagram.com pinterest.com disqus.com bitbucket.com rdio.com addons.mozilla.org
7. Features Object Relational Mapping (ORM) Automatic admin interface Elegent URL design Template system
8. Architecture
9. Model - View - Template Model - what things are View - how things are processed Template - How things are presented
10. Models import datetime from django.db import models from django.utils import timezone class Question(models.Model): question_text = models.CharField(max_length=200) pub_date = models.DateTimeField('date published') class Choice(models.Model): question = models.ForeignKey(Question) choice_text = models.CharField(max_length=200) votes = models.IntegerField(default=0)
11. Represents the DB objects BEGIN; CREATE TABLE "codecamp_question" ( "id" integer NOT NULL PRIMARY KEY, "question_text" varchar(200) NOT NULL, "pub_date" datetime NOT NULL ) ; CREATE TABLE "codecamp_choice" ( "id" integer NOT NULL PRIMARY KEY, "question_id" integer NOT NULL REFERENCES "codecamp_question" ("id"), "choice_text" varchar(200) NOT NULL, "votes" integer NOT NULL ) ; COMMIT;
12. ORM latest_question_list = Question.objects.order_by('-pub_date')[:5] q = Question.objects.get(pk=question_id) selected_choice = q.choice_set.get(pk=choice_id) selected_choice.votes += 1 selected_choice.save() Never write SQL - unless you really need
13. Views Where all magic happens Normally Keep your logic in the model Process model instances Render HTML
14. Views def vote(request, question_id): p = get_object_or_404(Question, pk=question_id) try: selected_choice = p.choice_set.get(pk=request.POST['choice']) except (KeyError, Choice.DoesNotExist): # Redisplay the question voting form. return render(request, 'polls/detail.html', { 'question': p, 'error_message': "You didn't select a choice.", }) else: selected_choice.votes += 1 selected_choice.save() return HttpResponseRedirect(reverse('results', args=(p.id,)))
15. Templates Separate design from code Separate designer from code Separate design from developers
16. index.html {% if latest_question_list %} <ul> {% for question in latest_question_list %} <li> <a href="{% url 'detail' question.id %}"> {{ question.question_text }} </a> </li> {% endfor %} </ul> {% else %} <p>No polls are available.</p> {% endif %}
17. views.py from django.shortcuts import render, get_object_or_404 from django.http import HttpResponseRedirect, HttpResponse from django.core.urlresolvers import reverse from codecamp.models import Question def index(request): latest_question_list = Question.objects.order_by('-pub_date')[:5] context = {'latest_question_list': latest_question_list} return render(request, 'polls/index.html', context)
18. detail.html <h1>{{ question.question_text }}</h1> {% if error_message %} <p><strong>{{ error_message }}</strong></p> {% endif %} <form action="{% url 'vote' question.id %}" method="post"> {% csrf_token %} {% for choice in question.choice_set.all %} <input type="radio" name="choice" id="choice{{ forloop.counter }}" value="{{ choice.id }}" /> <label for="choice{{ forloop.counter }}"> {{ choice.choice_text }} </label><br /> {% endfor %} <input type="submit" value="Vote" /> </form>
19. views.py from django.shortcuts import render, get_object_or_404 from django.http import HttpResponseRedirect, HttpResponse from django.core.urlresolvers import reverse from codecamp.models import Question def detail(request, question_id): question = get_object_or_404(Question, pk=question_id) return render(request, 'polls/detail.html', { 'question': question })
20. Security advantages No raw SQL from users - we deal with models and queries Automatic HTML parsing - no XSS attacks CSRF protection - no replay of forms by other code
21. URLs from django.conf.urls import patterns, include, url from codecamp import views # for admin page from django.contrib import admin admin.autodiscover() urlpatterns = patterns('', url(r'^$', views.index, name='index'), url(r'^polls/(?P<question_id>\d+)/$', views.detail, name='detail'), url(r'^polls/(?P<question_id>\d+)/results/$', views.results, name='results'), url(r'^polls/(?P<question_id>\d+)/vote/$', views.vote, name='vote'), url(r'^admin/', include(admin.site.urls)), ) URLs map to views (view Regular expressions)
22. http://example.com/ http://example.com/polls/1 http://example.com/polls/1/result http://example.com/polls/1/vote
23. Views are python function from django.shortcuts import render, get_object_or_404 from django.http import HttpResponseRedirect, HttpResponse from django.core.urlresolvers import reverse from codecamp.models import Question def detail(request, question_id): question = get_object_or_404(Question, pk=question_id) return render(request, 'polls/detail.html', { 'question': question })
24. Admin interface class ChoiceInline(admin.StackedInline): model = models.Choice extra = 4 class QuestionAdmin(admin.ModelAdmin): fieldsets = [ (None, {'fields': ['question_text']}), ('Date information', {'fields': ['pub_date']}), ] search_fields = ['question_text'] list_display = ('question_text', 'pub_date', 'was_published_recently') inlines = [ChoiceInline] admin.site.register(models.Question, QuestionAdmin)
25. Admin interface class MemberAdmin(UserAdmin): list_filter = ('is_admin', ) filter_horizontal = () fieldsets = ( (None, {'fields': ('username', 'password')}), (_('Personal info'), {'fields': ('email', )}), ) search_fields = ('email', 'username') list_display = ('username', 'email', 'is_admin', 'date_joined') list_per_page = 50 admin.site.register(models.Member, MemberAdmin) admin.site.register(models.Question, QuestionAdmin)
26. Other features Forms Generic Views User management Advance queries
27. manage.py shell: start up a python shell with your django project loaded in test: run you unit test runserver: run built in server for python app syncdb: create SQL for your models
28. Heroku
29. Features Support various programming language: Python, Ruby, Node.js, Java, Scala, ... Support a lot of plugins to work with other cloud services (AWS, RDS, MongoDB, ...) Painless deploy/rollback over git tool Easily to scale horizontally???
30. addons.heroku.com Worker hours Email services HTTPs Databases Message/Task Queue
31. Django over Heroku Procfile gunicorn requirements.txt
32. requirements.txt Django==1.5.1 dj-database-url==0.2.1 dj-static==0.0.5 gunicorn==17.5 psycopg2==2.5.1 static==0.4
33. Procfile web: gunicorn codecamp.wsgi
34. QA
35. References https://www.heroku.com/ https://www.djangoproject.com/ https://speakerdeck.com/kiennt/introduction-to- django