3、render使用添加命名空间抛出404错误

第三部分官网参考链接 https://docs.djangoproject.com/zh-hans/2.2/intro/tutorial03/
1、编写更多视图：
添加函数
polls/views.py

def detail(request, question_id):
    return HttpResponse("You're looking at question %s." % question_id)

def results(request, question_id):
    response = "You're looking at the results of question %s."
    return HttpResponse(response % question_id)

def vote(request, question_id):
    return HttpResponse("You're voting on question %s." % question_id)

url函数调用
polls/urls.py

from django.urls import path
from . import views
urlpatterns = [
    # ex: /polls/
    path('', views.index, name='index'),
        # ex: /polls/5
    path('<int:question_id>/', views.detail, name='detail'),
    # ex: /polls/5/results/
    path('<int:question_id>/results/', views.results, name='results'),
    # ex: /polls/5/vote/
    path('<int:question_id>/vote/', views.vote, name='vote'),
]

访问：
http://127.0.0.1:8000/polls/
http://127.0.0.1:8000/polls/5
http://127.0.0.1:8000/polls/5/results
http://127.0.0.1:8000/polls/5/vote

2、一个快捷函数： render()的使用
(1) 编写index视图

polls/views.py
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)

（2）添加模板
polls应用下创建templates/polls子文件夹，再在polls/templates/polls下创建index.html
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>No polls are available.</p>
{% endif %}

页面添加六条数据 http://127.0.0.1:8000/admin
测试访问：http://127.0.0.1:8000/polls/

3、一个快捷函数： get_object_or_404()抛出404错误
（1）编写视图

from django.shortcuts import get_object_or_404, render
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})

添加模板系统
polls/templates/polls/detail.html
{{ question }}

4、为 URL 名称添加命名空间
在每个应用的的urls下添加对应的应用名字的命名空间
polls/urls.py

from django.urls import path
from . import views
app_name = 'polls'   #添加命名空间
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'),
]

修改为指向具有命名空间的详细视图：
polls/templates/polls/index.html
<li><a href="{% url 'polls:detail' question.id %}">{{ question.question_text }}</a></li>