13分页和shell命令行模式

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1.为什么先讲分页功能

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：
- 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：
查询现有博客情况，如下图中的方法：

3.模型新增对象

>>> 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

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 blogE:\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... OKE:\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 instanceS.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>

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_listcontext['page_of_blogs'] = page_of_blogscontext['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_typecontext['blogs'] = Blog.objects.filter(blog_type=blog_type)context['blog_types'] = BlogType.objects.all()context['page_of_blogs'] = page_of_blogsreturn 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 %}