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A Basic Django Introduction


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A Basic Django Introduction

  1. 1. Web Development With Django A Basic Introduction Ganga L
  2. 2. Python Frameworks  Django  CherryPy  Pylons  Flask  Bottle  Tipfy  Pyramid  Cubic Web  GAE framework
  3. 3. Outline What Is Django? Project Structure Data Handling The Admin Interface Django Forms Views Templates
  4. 4. What Is Django? High-level framework for rapid web development Complete stack of tools Data modelled with Python classes Production-ready data admin interface, generated dynamically Elegant system for mapping URLs to Python code Generic views’ to handle common requests Clean, powerful template language Components for user authentication, form handling, caching . . .
  5. 5. Creating Projects & Apps Creating a project: startproject mysite Creating an app within a project directory: cd mysite ./ startapp poll
  6. 6. Project Structure A Python package on your PYTHONPATH Holds project-wide settings in Holds a URL configuration (URLconf) in Contains or references one or more apps
  7. 7. App A Python package on your PYTHONPATH (typically created as a subpackage of the project itself) May contain data models in May contain views in May have its own URL configuration in
  8. 8. Up & Running Set PYTHONPATH to include parent of your project directory Define new environment variable DJANGO_SETTINGS_MODULE, setting it to project settings (mysite.settings) 3 Try running the development server: / runserver
  9. 9. Creating The Database Create database polls in youe database Sync installed apps with database: ./ syncdb
  10. 10. Create Project Create Project mysite mysite/ mysite/
  11. 11. Create Application python startapp polls polls/
  12. 12. Create Models from django.db import models class Poll(models.Model): question = models.CharField(max_length=200) pub_date = models.DateTimeField(date published) class Choice(models.Model): poll = models.ForeignKey(Poll) choice_text = models.CharField(max_length=200) votes = models.IntegerField(default=0)
  13. 13. The Data Model  A description of database layout, as a Python class  Normally represents one database table  Has fields that map onto columns of the table  Many built-in field types  CharField, TextField  IntegerField, FloatField, DecimalField  DateField, DateTimeField, TimeField  EmailField, URLField  ForeignKey . . .
  14. 14. Installed App INSTALLED_APPS = ( django.contrib.admin, django.contrib.auth, django.contrib.contenttypes, django.contrib.sessions, django.contrib.messages, django.contrib.staticfiles, polls, ) python syncdb
  15. 15. Registering Models in Admin In in the Poll app: from django.contrib import admin from mysite.polls.models import Poll
  16. 16. In from django.conf.urls import patterns, include, url from django.contrib import admin admin.autodiscover() urlpatterns = patterns(, url(r^admin/, include(, )
  17. 17. Generic Views Provide ready-made logic for many common tasks:  Issuing a redirect  Displaying a paginated list of objects  Displaying a ‘detail’ page for a single object  Yearly, monthly or daily listing of date-based objects  ‘Latest items’ page for date-based objects  Object creation, updating, deletion (with/without authorisation)
  18. 18. Generic Views Example def index(request): return HttpResponse("Hello, world. Youre at the poll index.") from django.conf.urls.defaults import * from polls import views urlpatterns = patterns(, url(r^$, views.index, name=index) ) Main from django.conf.urls import patterns, include, url from django.contrib import admin admin.autodiscover() urlpatterns = patterns(, url(r^polls/, include(polls.urls)), url(r^admin/, include(, )
  19. 19. Creating & Saving Objects  Invoke constructor and call save method:  call create method of Club model manager:poll = Poll(question=what is your DOB? , year=1986) is your DOB? , year=1986)
  20. 20. View Function Takes an HTTPRequest object as a parameter Returns an HTTPResponse object to caller Is associated with a particular URL via the URLconf
  21. 21. HTTP Responsefrom datetime import datefrom django.http import HttpResponsedef today(request): html = <html><body><h2>%s</h2></body></html> % return HttpResponse(html)from django.shortcuts import render_to_responseFrom mysite.polls.models import Polldef poll_details(request): today = poll_data = Poll.objects.all() return render_to_response(clubs.html, locals(), context_instance = RequestContext(request))
  22. 22. Templates  Text files containing  Variables, replaced by values when the template is rendered[  {{ today }}  Filters that modify how values are displayed  {{ today|date:"D d M Y" }}  Tags that control the logic of the rendering process  {% if name == "nick" %}  <p>Hello, Nick!</p>  {% else %}  <p>Who are you?</p>  {% endif %}
  23. 23. Template Examplesettings.pyTEMPLATE_DIRS = ( os.path.join(os.path.dirname(__file__), templates), ) templates/club/club_list.html {% extends "base.html" %} {% block title %}Clubs{% endblock %} {% block content %} <h1>Clubs</h1> <ol> {% for club in clubs %} <li>{{ club }}</li> {% endfor %} </ol> {% endblock %}
  24. 24. Django Forms A collection of fields that knows how to validate itself and display itself as HTML. Display an HTML form with automatically generated form widgets. Check submitted data against a set of validation rules. Redisplay a form in the case of validation errors. Convert submitted form data to the relevant Python data types.
  25. 25. Django Model Forms from django.forms import ModelForm import mysite.polls.models import Poll class PollForm(ModelForm): class Meta: model = Pole
  26. 26. A Basic Django Forms
  27. 27. Standard
  28. 28. Standard
  29. 29. Standard
  30. 30. Easy
  31. 31. Easy
  32. 32. Summary We have shown you  The structure of a Django project  How models represent data in Django applications  How data can be stored and queried via model instances  How data can be managed through a dynamic admin interface  How functionality is represent by views, each associated with URLs that match a given pattern  How views render a response using a template
  33. 33. Thank You