以一个投票程序的实例来讲解Python的Django框架使用
（一）关于Django
Django是一个基于MVC构造的框架。但是在Django中，控制器接受用户输入的部分由框架自行处理，所以 Django 里更关注的是模型（Model）、模板(Template)和视图（Views），称为 MTV模式。
Ubuntu下的安装：一般都自带Python的。网上教程比较多了....
dizzy@dizzy-pc:~$ python Python 2.7.3 (default, Apr 20 2012, 22:44:07) [GCC 4.6.3] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> import django >>> help(django) VERSION = (1, 6, 4, 'final', 0) #可以查看django版本等信息。
（二）第一个Django的app
#环境：Python2.7，Django1.6，Ubuntu12.04
Python 及 Django 安装成功之后，就可以创建Django工程了
（1）教你开始写Django1.6的第1个app
#先创建一个文件夹 dizzy@dizzy-pc:~$ mkdir Python dizzy@dizzy-pc:~$ cd Python #然后创建工程 dizzy@dizzy-pc:~/Python$ django-admin.py startproject mysite dizzy@dizzy-pc:~/Python$ cd mysite #然后这个工程就可以启动服务了 dizzy@dizzy-pc:~/Python/mysite$ python manage.py runserver Validating models... 0 errors found July 23, 2014 - 14:17:29 Django version 1.6.4, using settings 'mysite.settings' Starting development server at http://127.0.0.1:8000/ Quit the server with CONTROL-C. #这样，打开浏览器访问： 便可看到： It Worked！ 关闭服务：ctrl+c #新创建的项目里面会有：manage.py文件，mysite文件夹 #在mysite文件夹里面会有：__init__.py,settings.py,urls.py,wsgi.py四个文件 #__init__.py是一个空文件， #setting.py 是项目的配置文件。需要修改两个地方，这里使用默认的SQLite3数据库 LANGUAGE_CODE = 'zh-cn' #原：en-us TIME_ZONE = 'Asia/Shanghai' #原：UTC #配置完之后，便可以创建数据表了 dizzy@dizzy-pc:~/Python/mysite$ python manage.py syncdb #创建是还要设置一个超级管理员，用于后台登录。 #设置完之后，开启服务，便可进入后台管理界面了：http://127.0.0.1:8000/admin/
（2）教你开始写Django1.6的第1个app
#创建一个用于投票的app。 #进入mysite工程根目录，创建app dizzy@dizzy-pc:~/Python/mysite$ python manage.py startapp polls dizzy@dizzy-pc:~/Python/mysite$ ls polls admin.py __init__.py models.py urls.py views.py #这样。Django已经生成了，app通常所需的模板文件。
下面创建两个models。Poll 和 Choice
dizzy@dizzy-pc:~/Python/mysite$ vim polls/models.py
修改文件如下：
from django.db import models
# Create your models here.
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)
#基本创建model过程就是这样，细节还要深入研究！
然后修改工程的配置文件setting.py,在INSTALLED_APP元组下面添加刚才创建的app：polls
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：
- “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！
要想使试图能被访问，还要配置 urls.py 。mysite是整个网站的URLConf，但每个app可以有自己的URLConf，通过include的方式导入到根配置中即可。现在在polls下面新建 urls.py
from django.conf.urls import patterns,url
from polls import views
urlpatterns = patterns('',
#ex:/polls/
url(r'^$',views.index,name='index'),
#ex:/polls/5/
url(r'^(?P<poll_id>\d+)/$',views.detail,name='detail'),
#ex:/polls/5/results/
url(r'^(?P<poll_id>\d+)/results/$',views.results,name='results'),
#ex:/polls/5/vote/
url(r'^(?P<poll_id>\d+)/vote/$',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！！！！！
然后在根 urls.py 文件中，include这个文件即可。
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'^$', 'mysite.views.home', name='home'),
# url(r'^blog/', include('blog.urls')),
url(r'^polls/', include('polls.urls',namespace="polls")),
url(r'^admin/', include(admin.site.urls)),
)
#有Example：两种形式。因为是元组，所以开始有“ ‘'， ”。
然后开始创建模板文件。在polls下，创建templates文件夹。下面有index.html, detail.html 两个文件。
<!-- index.html -->
{% if latest_poll_list %}
<ul>
{% for poll in latest_poll_list %}
<li><a href="{% url 'polls:detail' poll_id=poll.id %}">{{ poll.question }}</a></li>
{% endfor %}
</ul>
{% else %}
<p>No polls are available.</p>
{% endif %}
<!--detail.html-->
<h1 id="poll-question">{{ poll.question }}</h1>
<ul>
{% for choice in poll.choice_set.all %}
<li>{{ choice.choice_text }}</li>
{% endfor %}
</ul>
<!-- 视图设置完毕，具体语法还要深入研究！ -->
<!-- 现在重启服务， 便可看到相应视图 -->
（4）投票功能完善
上面只是简单的实现了视图功能，并没有真正的实现投票功能。接下来就是完善功能。
#修改模板文件
dizzy@dizzy-pc:~/Python/mysite$ vim polls/templates/polls/detail.html
#需要加入form表单
<h1 id="poll-question">{{ 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>
然后需要修改 views.py 中的 vote 处理函数。进行post数据的接收与处理。
# 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,)))
在投票成功之后，让用户浏览器重定向到结果 results.html 页。
def results(request, poll_id):
poll = get_object_or_404(Poll, pk=poll_id)
return render(request, 'polls/results.html', {'poll': poll})
然后就需要创建模板 results.html 。
<!-- polls/templates/polls/results.html -->
<h1 id="poll-question">{{ 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?</a>
至此，重启服务就能看到单选按钮，以及submit了。
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