13 分页和shell命令行模式

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1.为什么先讲分页功能

先讲分页功能，新增或编辑博客内容在admin后台操作.png

2.快速添加新的博客

• shell命令行模式下添加新博客：

  • python manage.py shell，如下图所示：

    
    进入shell命令行模式.png
  • for循环执行新增博客代码

• 添加一篇新的博客，涉及到Blog这个模型。因此在shell命令行模式下导入Blog这个模型。再用dir()方法来查看模型是否成功导入。如下图所示：

  
  导入Blog博客模型.png

• 查询现有博客情况，如下图中的方法：

  
  查询现有博客信息.png

3.模型新增对象

新增博客后的网页.png

>>> from blog.models import Blog
>>>
>>>
>>>
>>> Blog.objects.all()
<QuerySet [<Blog: <Blog: 长内容的博客>>, <Blog: <Blog: 人物介绍>>, <Blog: <Blog: Django简
介>>]
>>> Blog.objects.all().count()
3
>>> blog = Blog()


>>> Blog.objects.all()
<QuerySet [<Blog: <Blog: 长内容的博客>>, <Blog: <Blog: 人物介绍>>, <Blog: <Blog: Django简
介>>]>
>>> blog.title = "shell模式下的第一篇博客"
>>> blog.content = "这是一篇测试博客，233333333333333333333333333333333"
>>> from blog.models import BlogType
>>> dir()
['Blog', 'BlogType', '__builtins__', 'blog']

>>> BlogType.objects.all()
<QuerySet [<BlogType: Django>, <BlogType: 随笔>, <BlogType: 感悟>]>

>>> blog_type = BlogType.objects.all()[1]
>>> blog.blog_type = blog_type


>>> from django.contrib.auth.models import User
>>> User.objects.all()
<QuerySet [<User: CurryCoder>]>

>>> User.objects.all()
<QuerySet [<User: CurryCoder>]>
>>> user = User.objects.all()[0]
>>> blog.author = user


>>> blog.save()


>>> Blog.objects.all()
<QuerySet [<Blog: <Blog: 长内容的博客>>, <Blog: <Blog: 人物介绍>>, <Blog: <Blog: Django简
介>>, <Blog: <Blog: shell模式下的第一篇博客>>]>
>>> Blog.objects.all().count()
4
<!-- 查询blog对象的方法和属性 -->
>>> dir(blog)
['DoesNotExist', 'MultipleObjectsReturned', '__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getstate__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__setstate__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_check_column_name_clashes', '_check_field_name_clashes', '_check_fields', '_check_id_field', '_check_index_together', '_check_local_fields', '_check_long_column_names', '_check_m2m_through_same_relationship', '_check_managers', '_check_model', '_check_model_name_db_lookup_clashes', '_check_ordering', '_check_swappable', '_check_unique_together', '_do_insert', '_do_update', '_get_FIELD_display', '_get_next_or_previous_by_FIELD', '_get_next_or_previous_in_order', '_get_pk_val', '_get_unique_checks', '_meta', '_perform_date_checks', '_perform_unique_checks', '_save_parents', '_save_table', '_set_pk_val', '_state', 'author', 'author_id', 'blog_type', 'blog_type_id', 'check', 'clean', 'clean_fields', 'content', 'created_time', 'date_error_message', 'delete', 'from_db', 'full_clean', 'get_deferred_fields', 'get_next_by_created_time', 'get_next_by_last_updated_time', 'get_previous_by_created_time', 'get_previous_by_last_updated_time', 'id', 'last_updated_time', 'objects', 'pk', 'prepare_database_save', 'refresh_from_db', 'save', 'save_base', 'serializable_value', 'title', 'unique_error_message', 'validate_unique']
>>> blog.last_updated_time
datetime.datetime(2020, 5, 13, 13, 44, 45, 113603, tzinfo=<UTC>)

• shell命令行模式下，快速添加大批量博客。具体效果如下如所示：

  >>> for i in range(1,31):
  ...   blog = Blog()
  ...   blog.title = "for %s" % i
  ...   blog.content = "这是for循环生成的第%s篇博客" % i
  ...   blog.blog_type = blog_type
  ...   blog.author = user
  ...   blog.save()
  ...
  ...
  >>> Blog.objects.all().count()
  34
  

shell命令行模式下，快速添加大批量博客.png

4.分页器实现分页

• 通过上图我们可以看出，当一下显示所有的博客时。因此实现分页功能，更便于我们查看想要浏览的博客。

  >>> del Blog  # 删除某个模型
  >>> Blog
  Traceback (most recent call last):
    File "<console>", line 1, in <module>
  NameError: name 'Blog' is not defined
  >>> exit()
  >>> python manage.py shell
  >>> dir()
  ['__builtins__']
  >>> from django.core.paginator import Paginator
  >>> from blog.models import Blog
  >>> Blog.objects.all()
  <QuerySet [<Blog: <Blog: 长内容的博客>>, <Blog: <Blog: 人物介绍>>, <Blog: <Blog: Django简
  介>>, <Blog: <Blog: shell模式下的第一篇博客>>, <Blog: <Blog: for 1>>, <Blog: <Blog: for 2>
  >, <Blog: <Blog: for 3>>, <Blog: <Blog: for 4>>, <Blog: <Blog: for 5>>, <Blog: <Blog: for 6>>, <Blog: <Blog: for 7>>, <Blog: <Blog: for 8>>, <Blog: <Blog: for 9>>, <Blog: <Blog: for 10>>, <Blog: <Blog: for 11>>, <Blog: <Blog: for 12>>, <Blog: <Blog: for 13>>, <Blog: <Blog: for 14>>, <Blog: <Blog: for 15>>, <Blog: <Blog: for 16>>, '...(remaining elements truncated)...']>
  >>> blogs = Blog.objects.all()
  >>> blogs.count()
  34
  >>> paginator = Paginator(blogs, 10)
  <string>:1: UnorderedObjectListWarning: Pagination may yield inconsistent results with an unordered object_list: <class 'blog.models.Blog'> QuerySet.
  

• 出现上面的UnorderedObjectListWarning错误，这是由于没有设置分页后每一页按照什么顺序排序。因此打开blog目录下的models.py文件，在Blog类下添加Meta类如下所示：

  from django.db import models
  from django.contrib.auth.models import User
  
  # Create your models here.
  
  # 创建博文类型模型
  
  
  class BlogType(models.Model):
      type_name = models.CharField(max_length=15)
  
      def __str__(self):
          return self.type_name
  
  # 创建博文模型
  
  
  class Blog(models.Model):
      title = models.CharField(max_length=50)
      # 一篇博文属于一种类型,因此博客通过外键关联到博文类型
      blog_type = models.ForeignKey(BlogType, on_delete=models.DO_NOTHING)
      content = models.TextField()
      author = models.ForeignKey(User, on_delete=models.DO_NOTHING)
      created_time = models.DateTimeField(auto_now_add=True)
      last_updated_time = models.DateTimeField(auto_now=True)
  
      def __str__(self):
          return "<Blog: %s>" % self.title
      <!-- 添加的新内容 -->
      class Meta:
          ordering = ['-created_time']
  

• 由于已经修改了Blog模型，所以要进行同步数据库。输入如下命令，如下图所示：

  E:\Django\mysite_env\Scripts\mysite
  $ python manage.py makemigrations
  Migrations for 'blog':
    blog\migrations\0003_auto_20200513_2224.py
      - Change Meta options on blog
  
  E:\Django\mysite_env\Scripts\mysite
  $ python manage.py migrate
  Operations to perform:
    Apply all migrations: admin, auth, blog, contenttypes, sessions
  Running migrations:
    Applying blog.0003_auto_20200513_2224... OK
  
  E:\Django\mysite_env\Scripts\mysite
  $ python manage.py runserver
  Performing system checks...
  
  System check identified no issues (0 silenced).
  May 13, 2020 - 22:24:47
  Django version 2.0, using settings 'mysite.settings'
  Starting development server at http://127.0.0.1:8000/
  Quit the server with CTRL-BREAK.
  

• 退出之前的shell命令行模型，重新进入shell命令行模式下，输入如下代码：

  >>> from django.core.paginator import Paginator
  >>> from blog.models import Blog
  >>> blogs = Blog.objects.all()
  >>> paginator = Paginator(blogs, 10)
  >>> paginator
  <django.core.paginator.Paginator object at 0x000000000469D978>
  >>> dir(paginator)
  ['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_check_object_list_is_ordered', '_get_page', 'allow_empty_first_page', 'count', 'get_page', 'num_pages', 'object_list', 'orphans', 'page', 'page_range', 'per_page', 'validate_number']
  >>> paginator.__doc__
  >>> paginator.count
  34
  >>> paginator.num_pages
  4
  >>> paginator.page_range
  range(1, 5)
  >>>
  >>> page1 = paginator.page(1)
  >>> page1
  <Page 1 of 4>
  >>> dir(page1)
  ['__abstractmethods__', '__class__', '__contains__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__gt__', '__hash__', '__init__', '__iter__', '__le__', '__len__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__setattr__', '__sizeof__', '__slots__', '__str__', '__subclasshook__', '__weakref__', '_abc_cache', '_abc_negative_cache', '_abc_negative_cache_version', '_abc_registry', 'count', 'end_index', 'has_next', 'has_other_pages', 'has_previous', 'index', 'next_page_number', 'number', 'object_list', 'paginator', 'previous_page_number', 'start_index']
  >>> page1.count
  <bound method Sequence.count of <Page 1 of 4>>
  >>> help(page1.count)
  Help on method count in module collections.abc:
  
  count(value) method of django.core.paginator.Page instance
      S.count(value) -> integer -- return number of occurrences of value
  >>>
  >>> page1.object_list
  [<Blog: <Blog: for 30>>, <Blog: <Blog: for 29>>, <Blog: <Blog: for 28>>, <Blog: <Blog: for 27>>, <Blog: <Blog: for 26>>, <Blog: <Blog: for 25>>, <Blog: <Blog: for 24>>, <Blog: <Blog: for 23>>, <Blog: <Blog: for 22>>, <Blog: <Blog: for 21>>]
  >>> page1.object_list.count
  <built-in method count of list object at 0x00000000046AFDC8>
  

  分页器实现分页.png

5.分页的使用

• 前端页面：向后端服务器发送请求，请求打开具体的分页内容；
• 后端服务器：处理请求，返回具体分页内容响应请求；
• 例如，可以通过在浏览器中输入localhost:8000/blog/?page=1来访问第一页中的所有方法。因为前端通过url向服务器发送了GET请求，所以打开blog文件目录下的views.py文件，在blog_list()和blogs_with_type()函数中增加该请求对应的方法。views.py文件的内容如下：

  from django.shortcuts import render_to_response, get_object_or_404
  from django.core.paginator import Paginator
  from .models import Blog, BlogType
  # Create your views here.
  
  
  def blog_list(request):
      blogs_all_list = Blog.objects.all()
      paginator = Paginator(blogs_all_list, 10)  # 每10篇进行一次分页
      page_num = request.GET.get('page', 1)  # 获取url的页码参数(GET请求)
      page_of_blogs = paginator.get_page(page_num)
  
      context = {}
      context['blogs'] = page_of_blogs.object_list
      context['page_of_blogs'] = page_of_blogs
      context['blog_types'] = BlogType.objects.all()
      return render_to_response('blog/blog_list.html', context)
  
  
  def blog_detail(request, blog_pk):
      context = {}
      context['blog'] = get_object_or_404(Blog, pk=blog_pk)
      return render_to_response('blog/blog_detail.html', context)
  
  
  def blogs_with_type(request, blog_type_pk):
      blogs_all_list = Blog.objects.all()
      paginator = Paginator(blogs_all_list, 2)  # 每2篇进行一次分页
      page_num = request.GET.get('page', 1)  # 获取url的页码参数(GET请求)
      page_of_blogs = paginator.get_page(page_num)
  
      context = {}
      blog_type = get_object_or_404(BlogType, pk=blog_type_pk)
      context['blog_type'] = blog_type
      context['blogs'] = Blog.objects.filter(blog_type=blog_type)
      context['blog_types'] = BlogType.objects.all()
      context['page_of_blogs'] = page_of_blogs
      return render_to_response('blog/blogs_with_type.html', context)
  

• 接着，修改blog文件目录下的templates文件夹下的blog_list.html模板文件，经过views.py处理请求后，返回新的结果给前端页面。blog_list.html修改后的结果如下所示：

  {% extends 'base.html' %}
  {# blog_list.html文件内容 #}
  {# 页面标题 #}
  {% block title %}我的网站{% endblock %}
  {% block nav_blog_active %}active{% endblock %}
  
  {% load staticfiles %}
  {% block header_extends %}
      <link rel="stylesheet" href="{% static 'blog/blog.css' %}">
  {% endblock %}
  
  {# 页面内容 #}
  {% block content %}
      <div class="container">
          <div class="row">
              <div class="col-xs-12 col-sm-8 col-md-9 col-lg-10">
                  <div class="panel panel-default">
                      <div class="panel-heading">
                          {% block blog_list_title %}博客列表(一共有{{ page_of_blogs.paginator.count }}篇博客){% endblock %}
                      </div>
                      <div class="panel-body">
                          <!-- 下一行中的blogs来自于views.py中的context['blogs'] = Blog.objects.all() -->
                          {% for blog in blogs %}
                              <div class="blog">
                                  <!-- 下一行中的blog.title来自于models.py中的title = models.CharField(max_length=50) -->
                                  <h3><a href="{% url 'blog_detail' blog.pk %}">{{ blog.title }}</a></h3>
                                  <p class="blog-info">
                                      <span class="glyphicon glyphicon-tag"></span><a href="{% url 'blogs_with_type' blog.blog_type.pk %}">{{ blog.blog_type }}</a> &nbsp&nbsp&nbsp
                                      <span class="glyphicon glyphicon-time"></span>{{ blog.created_time|date:"Y-m-d" }}
                                  </p>
                                  <p>{{ blog.content|truncatechars:120 }}</p>
                              </div>
                          {% empty %}
                             <div class="bog">
                                  <h3>暂无博客，敬请期待</h3>
                             </div>
                          {% endfor %}
                      </div>
                  </div>
                  <!-- 此处使用了bootstrp组件中的分页代码 -->
                  <div>
                      <ul class="pagination">
                          {# 上一页 #}
                          <li>
                              {% if page_of_blogs.has_previous %}
                                  <a href="?page={{ page_of_blogs.previous_page_number }}" aria-label="Previous">
                                      <span aria-hidden="true">&laquo;</span>
                                  </a>
                              {% else %}
                                  <span aria-hidden="true">&laquo;</span>
                              {% endif %}
  
                          </li>
  
                          {# 全部页码 #}
                          {% for page_num in page_of_blogs.paginator.page_range %}
                              <li><a href="?page={{ page_num }}">{{ page_num }}</a></li>
                          {% endfor %}
  
                          {# 下一页 #}
                          <li>
                              {% if page_of_blogs.has_next %}
                                  <a href="?page={{ page_of_blogs.next_page_number }}" aria-label="Next">
                                      <span aria-hidden="true">&raquo;</span>
                                  </a>
                              {% else %}
                                  <span aria-hidden="true">&raquo;</span>
                              {% endif %}
                          </li>
                      </ul>
                  </div>
  
  
  
              </div>
  
              <div class="hidden-xs col-sm-4 col-md-3 col-lg-2">
                  <div class="panel panel-default">
                      <div class="panel-heading">
                          博客分类
                      </div>
                      <div class="panel-body">
                          <ul class="blog-types">
                              {% for blog_type in blog_types %}
                                  <li><a href="{% url 'blogs_with_type' blog_type.pk %}">{{ blog_type.type_name }}</a></li>
                              {% empty %}
                                  <li>暂无分类</li>
                              {% endfor %}
                          </ul>
                      </div>
                  </div>
              </div>
          </div>
      </div>
  
  {% endblock %}
  

添加分页按钮后的前端页面.png