一.安装与项目的创建
1.安装
pip install django
2.查看版本
python -m django --version
3.创建项目
django-admin startproject mysite
manage.py 实用的与django项目进行交互的命令行工具
mysite 项目中的实际python包
mysite/__init__.py 空文件,表示这是一个python包
mysite/settings.py 此项目的配置文件
mysite/urls.py url声明文件
mysite/wsgi.py wsgi服务器的配置文件
4.启动开发模式下的服务器
python manage.py runserver 0.0.0.0:8000
浏览器访问:http://127.0.0.1:8000/
5.创建应用
在manage.py的同级目录下执行:
python manage.py startapp molin
6.第一个视图文件
polls/views.py
#_*_coding:utf8_*_ from django.shortcuts import HttpResponse def index(request): return HttpResponse("你好,欢迎来到投票系统的主页")
7.配置URL
新增polls/urls.py文件
#_*_coding:utf8_*_ from django.urls import path from . import views urlpatterns = [ path('', views.index, name='index'), ]
8.将polls/urls.py引入到mysite/urls.py文件中, 因为所有的url配置入口都是源于mysite/urls.py
mysite/urls.py
from django.contrib import admin from django.urls import path, include urlpatterns = [ path('polls/', include('polls.urls')), path('admin/', admin.site.urls), ]
path('polls/', include('polls.urls'))
, 然后读到polls/urls.py的配置:path('', views.index, name='index')
, 从而去执行polls/views.py的index方法二.模型与数据库的交互
1.数据库的设置
DATABASES = { 'default': { 'ENGINE': 'django.db.backends.sqlite3', 'NAME': os.path.join(BASE_DIR, 'db.sqlite3'), } }
有些应用要求我们必须至少要有一个数据库,如,django的后台,因此,让我们先来执行以下命令: $ python manage.py migrate
将django激活的应用所需的数据表创建好
2.创建模型
polls/models.py
#_*_coding:utf8_*_ from django.db import models 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, on_delete=models.CASCADE) choice_text = models.CharField(max_length=200) votes = models.IntegerField(default=0)
类中的每个属性映射为一个字段,并标识了这些字段的类型
3.激活模型
mysite/settings.py
INSTALLED_APPS = [ 'polls.apps.PollsConfig', # ... ]
4.生成迁移
$ python manage.py makemigrations polls
自动生成了polls/migrations/0001_initial.py文件,现在还没有真正创建数据表,需要再执行数据迁移才能生成数据表
执行迁移:$ python manage.py migrate
5.让django的命令行交互更友好
polls/models.py
from django.db import models class Question(models.Model): # ... def __str__(self): return self.question_text class Choice(models.Model): # ... def __str__(self): return self.choice_text
__str__()
函数将会返回我们定义好的数据格式。此外,我们还可以在models中添加自定义方法:
import datetime from django.db import models from django.utils import timezone class Question(models.Model): # ... def was_published_recently(self): return self.pub_date >= timezone.now() - datetime.timedelta(days=1)
6.进入交互模式对数据库进行操作
$ python manage.py shell
In [1]: from polls.models import Question, Choice In [2]: Question.objects.all() # 获取所有问题 Out[2]: <QuerySet [<Question: 问题2>]> In [3]: Question.objects.filter(id=1) # 获取id为1的数据 Out[3]: <QuerySet [<Question: 问题2>]> In [8]: Question.objects.filter(question_text__startswith='问题') # 获取内容包含'问题'的数据 Out[8]: <QuerySet [<Question: 问题2>]> In [9]: from django.utils import timezone In [10]: current_year = timezone.now().year In [11]: Question.objects.get(pub_date__year=current_year) Out[11]: <Question: 问题2> In [12]: Question.objects.get(id=2) # 当获取的数据不存在时,会报以下错误 --------------------------------------------------------------------------- DoesNotExist Traceback (most recent call last) <ipython-input-12-75091ca84516> in <module>() ----> 1 Question.objects.get(id=2) In [13]: Question.objects.get(pk=1) Out[13]: <Question: 问题2> In [14]: q = Question.objects.get(pk=1) In [15]: q.was_published_recently() # 调用自定义的方法 Out[15]: True In [16]: q = Question.objects.get(pk=1) In [17]: q.choice_set.all() Out[17]: <QuerySet []> In [19]: q.choice_set.create(choice_text='选项1', votes=0) Out[19]: <Choice: 选项1> In [20]: q.choice_set.create(choice_text='选项2', votes=0) Out[20]: <Choice: 选项2> In [21]: c = q.choice_set.create(choice_text='选项3', votes=0) In [22]: c.question Out[22]: <Question: 问题2> In [23]: q.choice_set.all() Out[23]: <QuerySet [<Choice: 选项1>, <Choice: 选项2>, <Choice: 选项3>]> In [24]: q.choice_set.count() Out[24]: 3 In [25]: Choice.objects.filter(question__pub_date__year=current_year) Out[25]: <QuerySet [<Choice: 选项1>, <Choice: 选项2>, <Choice: 选项3>]> In [26]: c = q.choice_set.filter(choice_text__startswith='选项3') In [27]: c.delete() Out[27]: <bound method QuerySet.delete of <QuerySet [<Choice: 选项3>]>> In [29]: Choice.objects.filter(question__pub_date__year=current_year) Out[29]: <QuerySet [<Choice: 选项1>, <Choice: 选项2>]>
7.创建后台管理员
django自带了一个管理后台,我们只需创建一个管理员用户即可使用
创建一个后台管理员用户: $ python manage.py createsuperuser
8.引入模型
polls/admin.py
#_*_coding:utf8_*_ from django.contrib import admin from .models import Question admin.site.register(Question)
登陆后台可以对模型进行操作
三.视图views和模板template的操作
1.django的视图用于处理url请求,并将响应的数据传递到模板,最终浏览器将模板数据进行渲染显示,用户就得到了想要的结果
增加视图:polls/views.py
#_*_coding:utf8_*_ from django.shortcuts import HttpResponse def index(request): return HttpResponse("你好,欢迎来到投票系统的主页") def detail(request, question_id): return HttpResponse('你正在查看问题%s' % question_id) def results(request, question_id): response = '你正在查看问题%s的结果' return HttpResponse(response % question_id) def vote(request, question_id): return HttpResponse('你正在给问题%s投票' % question_id)
配置url:polls/urls.py
#_*_coding:utf8_*_ from django.urls import path from . import views urlpatterns = [ # /polls/ path('', views.index, name='index'), # /polls/1/ path('<int:question_id>/', views.detail, name='detail'), # /polls/1/results/ path('<int:question_id>/results/', views.results, name='results'), # /polls/1/vote/ path('<int:question_id>/vote/', views.vote, name='vote'), ]
2.通过视图直接返回的数据,显示格式很单一,要想显示丰富的数据形式,就需要引用模板,用独立的模板文件来呈现内容。
新增模板:polls/templates/polls/index.html
{% if latest_question_list %} <ul> {% for question in latest_question_list %} <li><a href="/polls/{{question.id}}/">{{question.question_text}}</a></li> {% endfor %} </ul> {% else %} <p>问题为空</p> {% endif %}
修改视图: polls/views.py 传递变量给模板
#_*_coding:utf8_*_ from django.shortcuts import HttpResponse from django.template import loader from .models import Question def index(request): latest_question_list = Question.objects.order_by('-pub_date')[:5] template = loader.get_template('polls/index.html') context = {'latest_question_list': latest_question_list} return HttpResponse(template.render(context, request))
开发中,直接使用render()即可,尽可能精简代码
from django.shortcuts import render from .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)
详情页的展示:polls/views.py
from django.http import Http404 from django.shortcuts import render from .models import Question # ... def detail(request, question_id): try: question = Question.objects.get(pk=question_id) except Question.DoesNotExist: raise Http404('问题不存在') return render(request, 'polls/detail.html', {'question': question})
404页面抛出的便捷写法:get_object_or_404()
polls/views.py
from django.shortcuts import render, get_object_or_404 from .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})
详情页输出关联数据表:
<h1>{{ question.question_text }}</h1> <ul> {% for choice in question.choice_set.all %} <li>{{ choice.choice_text }}</li> {% endfor %} </ul>
3.优化
去掉url的硬编码格式
<li><a href="{% url 'detail' question.id %}">{{question.question_text}}</a></li>
修改url配置
path('<int:question_id>/', views.detail, name='detail')
改为:此时,index.html的url会自动由 http://127.0.0.1:8000/polls/1/ 转为 http://127.0.0.1:8000/polls/specifics/1/
4.一个项目中多个应用的区分需要使用命名空间
#_*_coding:utf8_*_ from django.urls import path from . import views app_name = 'polls' urlpatterns = [ path('', views.index, name='index'), path('<int:question_id>/', views.detail, name='detail'), path('<int:question_id>/results/', views.results, name='results'), path('<int:question_id>/vote/', views.vote, name='vote'), ]
将index.html的url生成代码加上命名空间:
<li><a href="{% url 'polls:detail' question.id %}">{{question.question_text}}</a></li>
四.在前台进行投票操作
1.构建一个简单的表单提交页
polls/templates/polls/detail.html
<h1>{{ question.question_text }}</h1> {% if error_message %}<p><strong>{{ error_message }}</strong></p>{% endif %} <form action="{%url 'polls:vote' question.id %}" method="post"> {% csrf_token %} {% for choice in question.choice_set.all %} <input id="choice{{ forloop.counter }}" type="radio" name="choice" value="{{ choice.id }}"> <label for="choice{{ forloop.counter }}">{{ choice.choice_text }}</label><br /> {% endfor %} <br /> <input type="submit" name="" id="" value="投票" /> </form>
代码解析:
form表单提交的url为{%url 'polls:vote' question.id %}, 即表示访问polls/views.py的vote方法,并携带问题id作为参数。
将问题的相关选项遍历,以单选框显示
form表单用post方式提交数据
配置url: polls/urls.py
path('<int:question_id>/vote/', views.vote, name='vote'),
2.视图层处理提交结果
polls/views.py
from django.shortcuts import render, get_object_or_404 from django.http import HttpResponse, HttpResponseRedirect from django.urls import reverse from .models import Question, Choice # ... def vote(request, question_id): question = get_object_or_404(Question, pk=question_id) try: selected_choice = question.choice_set.get(pk=request.POST['choice']) except (KeyError, Choice.DoesNotExist): return render(request, 'polls/detail.html', { 'question': question, 'error_message': "必须选择一个选项", }) else: selected_choice.votes += 1 selected_choice.save() return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))
代码解析:
request.POST['choice']接收表单页面提交的数据
将投票次数加1,并更新数据库
3.显示投票结果
polls/views.py
from django.shortcuts import render, get_object_or_404 # ... def results(request, question_id): question = get_object_or_404(Question, pk=question_id) return render(request, 'polls/results.html', {'question': question})
results.html
<h1>{{ question.question_text }}</h1> <ul> {% for choice in question.choice_set.all %} <li>{{ choice.choice_text }} -- {{choice.votes}}</li> {% endfor %} </ul> <a href="{% url 'polls:detail' question.id %}">再投一次?</a>
4.优化url和view写法
将主键id代替question_id
polls/urls.py
#_*_coding:utf8_*_ from django.urls import path from . import views app_name = 'polls' urlpatterns = [ path('', views.IndexView.as_view(), name='index'), path('<int:pk>/', views.DetailView.as_view(), name='detail'), path('<int:pk>/results/', views.ResultsView.as_view(), name='results'), path('<int:question_id>/vote/', views.vote, name='vote'), ]
使用<pk>
代替<question_id>
会更加灵活,<pd>
代表主键
相应的视图也需要修改成另一种写法,vote方法保持原样,用于比较两种写法的不同
polls/views.py
#_*_coding:utf8_*_ from django.shortcuts import render, get_object_or_404 from django.http import HttpResponseRedirect from django.urls import reverse from django.views import generic from .models import Question, Choice class IndexView(generic.ListView): template_name = 'polls/index.html' context_object_name = 'latest_question_list' def get_queryset(self): return Question.objects.order_by('-pub_date')[:5] class DetailView(generic.DetailView): model = Question template_name = 'polls/detail.html' class ResultsView(generic.DetailView): model = Question template_name = 'polls/results.html' def vote(request, question_id): # ...