Introduction to Django v2

Introduction to django and deploy to self-hosted server

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. Features Object Relational Mapping (ORM) Automatic admin interface Elegent URL design Template system
7. Architecture
8. Model - View - Template Model - what things are View - how things are processed Template - How things are presented
9. 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)
10. 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;
11. 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
12. Views Where all magic happens Normally Keep your logic in the model Process model instances Render HTML
13. 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,)))
14. Templates Separate design from code Separate designer from code Separate design from developers
15. 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 %}
16. 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)
17. 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>
18. 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 })
19. 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
20. 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)
21. http://example.com/ http://example.com/polls/1 http://example.com/polls/1/result http://example.com/polls/1/vote
22. 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 })
23. 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)
24. 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)
25. Other features Forms Generic Views User management Advance queries
26. 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
27. Deploy
28. requirements zero downtime can rollback to old deployments
29. tools fabric to distribute code to server uWSGI - similar gunicorn but write in C, and support a lot of features
30. nginx uWSGI Django App Django App Django App
31. folders structure current -> /srv/sample_app/releases/c31245.... /srv/sample_app/ /releases /c31245 /d98818
32. deployment with rollback each release folder is snapshot of a git commit each release contain it own virtual environment isolate releases about python package, not system package !?
33. zero downtime uWSIG support autoload by watching changing of a file or folder when deploy new release write to new file
34. def release_commit(commit): code_dir = '/srv/simpleprints/base' new_release_dir = '/srv/simpleprints/releases/%s' % commit # create new release dir run('rm -rf %s' % new_release_dir) run('mkdir -p %s' % new_release_dir) with cd(code_dir): run('git archive %s | tar -C %s -xf -' % (commit, new_release_dir)) remove_old_release() # create virtualenv with cd(new_release_dir): run('virtualenv venv') # install with virtualenv('%s/venv/' % new_release_dir): run('pip install -r %s/requirements.txt' % new_release_dir) run('chown -R kiennt %s' % new_release_dir) reload_uwsgi_for_commit(commit)
35. QA