以一个投票程序的实例来讲解Python的Django框架使用

dizzy@dizzy-pc:~/Python/mysite$ vim mysite/settings.py
 
INSTALLED_APPS = (
  'django.contrib.admin',
  'django.contrib.auth',
  'django.contrib.contenttypes',
  'django.contrib.sessions',
  'django.contrib.messages',
  'django.contrib.staticfiles',
  'polls',
)
 
#可以使用 python manage.py sql polls 查看app的建表SQL
#使用 python manage.py syncdb 进行创建数据库表
dizzy@dizzy-pc:~/Python/mysite$ ./manage.py sql polls
BEGIN;
CREATE TABLE "polls_poll" (
  "id" integer NOT NULL PRIMARY KEY,
  "question" varchar(200) NOT NULL,
  "pub_date" datetime NOT NULL
)
;
CREATE TABLE "polls_choice" (
  "id" integer NOT NULL PRIMARY KEY,
  "poll_id" integer NOT NULL REFERENCES "polls_poll" ("id"),
  "choice_text" varchar(200) NOT NULL,
  "votes" integer NOT NULL
)
;
 
COMMIT;
 
#这样就可以通过设置model让Django自动创建数据库表了
    要想在后台admin中管理polls。还需要修改app下面的admin.py 文件。

from django.contrib import admin
 
# Register your models here.
 
from django.contrib import admin
from polls.models import Choice,Poll
 
class ChoiceInLine(admin.StackedInline):
  model = Choice
  extra = 3
 
class PollAdmin(admin.ModelAdmin):
  fieldsets = [
    (None,         {'fields':['question']}),
    ('Date information',  {'fields':['pub_date'],'classes':['collapse']}),
  ]
  inlines = [ChoiceInLine]
 
admin.site.register(Poll,PollAdmin)
 
#这部分代码，大体能看懂，具体的规则还要稍后的仔细研究。
##这部分代码，由于拼写失误，导致多处出错。细节决定成败！！

        这样再重启服务，就能在后台管理polls应用了。

（3）视图和控制器部分

            前面已经完成了model（M）的设置。剩下的只有view（V）和urls（C）了。Django的视图部分，由views.py 和 templates完成。

            在polls中，我们将创建4个视图：

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• “index” 列表页 – 显示最新投票。
• “detail” 投票页 – 显示一个投票的问题, 以及用户可用于投票的表单。
• “results” 结果页 – 显示一个投票的结果。
• 投票处理 – 对用户提交一个投票表单后的处理。

            现在修改 views.py 创建用于视图的函数。

dizzy@dizzy-pc:~/Python/mysite$ vim polls/views.py

from django.shortcuts import render,get_object_or_404
 
# Create your views here.
from django.http import HttpResponse
from polls.models import Poll
 
def index(request):
  latest_poll_list = Poll.objects.all().order_by('-pub_date')[:5]
  context = {'latest_poll_list':latest_poll_list}
  return render(request,'polls/index.html',context)
 
def detail(request,poll_id):
  poll = get_object_or_404(Poll,pk=poll_id)
  return render(request,'polls/detail.html',{'poll':poll})
 
def results(request,poll_id):
  return HttpResponse("you're looking at the results of poll %s." % poll_id)
 
def vote(request,poll_id):
  return HttpResponse("you're voting on poll %s." % poll_id)
 
#涉及Django的自带函数，不做深究。后面再做研究！

from django.conf.urls import patterns,url
 
from polls import views
 
urlpatterns = patterns('',
  #ex:/polls/
  url(r'^$',views.index,name='index'),
  #ex:/polls/5/
  url(r'^(&#63;P<poll_id>\d+)/$',views.detail,name='detail'),
  #ex:/polls/5/results/
  url(r'^(&#63;P<poll_id>\d+)/results/$',views.results,name='results'),
  #ex:/polls/5/vote/
  url(r'^(&#63;P<poll_id>\d+)/vote/$',views.vote,name='vote'),
)
#url中，三个参数。正则的url，处理的函数，以及名称
#正则表达式！！！！！

dizzy@dizzy-pc:~/Python/mysite$ vim mysite/urls.py

from django.conf.urls import patterns, include, url
 
from django.contrib import admin
admin.autodiscover()
 
urlpatterns = patterns('',
  # Examples:
  # url(r'^$', 'mysite.views.home', name='home'),
  # url(r'^blog/', include('blog.urls')),
 
  url(r'^polls/', include('polls.urls',namespace="polls")),
  url(r'^admin/', include(admin.site.urls)),
)
#有Example：两种形式。因为是元组，所以开始有“ ‘'， ”。

<!-- index.html -->
{% if latest_poll_list %}
  <ul>
  {% for poll in latest_poll_list %}
    <li><a href="{% url 'polls:detail' poll_id=poll.id %}">{{ poll.question }}</a></li>
  {% endfor %}
  </ul>
{% else %}
  <p>No polls are available.</p>
{% endif %}
 
<!--detail.html-->
<h1>{{ poll.question }}</h1>
<ul>
{% for choice in poll.choice_set.all %}
  <li>{{ choice.choice_text }}</li>
{% endfor %}
</ul>
 
<!-- 视图设置完毕，具体语法还要深入研究！ -->
<!-- 现在重启服务， 便可看到相应视图 -->

#修改模板文件
dizzy@dizzy-pc:~/Python/mysite$ vim polls/templates/polls/detail.html
#需要加入form表单

<h1>{{ poll.question }}</h1>
 
{% if error_message %}<p><strong>{{ error_message }}</strong></p>{% endif %}
 
<form action="{% url 'polls:vote' poll.id %}" method="post">
{% csrf_token %}
{% for choice in poll.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>

# 文件 polls/views.py
 
from django.shortcuts import get_object_or_404, render
from django.http import HttpResponseRedirect, HttpResponse
from django.core.urlresolvers import reverse
from polls.models import Choice, Poll
# ...
def vote(request, poll_id):
  p = get_object_or_404(Poll, pk=poll_id)
  try:
    selected_choice = p.choice_set.get(pk=request.POST['choice'])
  except (KeyError, Choice.DoesNotExist):
    # Redisplay the poll voting form.
    return render(request, 'polls/detail.html', {
      'poll': p,
      'error_message': "You didn't select a choice.",
    })
  else:
    selected_choice.votes += 1
    selected_choice.save()
    # Always return an HttpResponseRedirect after successfully dealing
    # with POST data. This prevents data from being posted twice if a
    # user hits the Back button.
    return HttpResponseRedirect(reverse('polls:results', args=(p.id,)))

def results(request, poll_id):
  poll = get_object_or_404(Poll, pk=poll_id)
  return render(request, 'polls/results.html', {'poll': poll})

<!-- polls/templates/polls/results.html -->
 
<h1>{{ poll.question }}</h1>
 
<ul>
{% for choice in poll.choice_set.all %}
  <li>{{ choice.choice_text }} -- {{ choice.votes }} vote{{ choice.votes|pluralize }}</li>
{% endfor %}
</ul>
 
<a href="{% url 'polls:detail' poll.id %}">Vote again&#63;</a>