分页器

自定义分页器

自定义分页器的使用,建立一个用来存储外来的组件(utils), 建一个py文件将代码直接拷贝过去

# @Author   :SkyOcean  # @Time:2019/10/2914:06
# @File     :mypage.py
class Pagination(object):
    def __init__(self, current_page, all_count, per_page_num=5, pager_count=11):
        """
        封装分页相关数据
        :param current_page: 当前页:current_page = request.GET.get('page',1)
        :param all_count:    数据库中的数据总条数
        :param per_page_num: 每页显示的数据条数
        :param pager_count:  最多显示的页码个数

        用法:
        queryset = model.objects.all()
        page_obj = Pagination(current_page,all_count)
        page_data = queryset[page_obj.start:page_obj.end]
        获取数据用page_data而不再使用原始的queryset
        获取前端分页样式用page_obj.page_html
        """
        try:
            current_page = int(current_page)
        except Exception as e:
            current_page = 1

        if current_page < 1:
            current_page = 1

        self.current_page = current_page

        self.all_count = all_count
        self.per_page_num = per_page_num

        # 总页码
        all_pager, tmp = divmod(all_count, per_page_num)
        if tmp:
            all_pager += 1
        self.all_pager = all_pager

        self.pager_count = pager_count
        self.pager_count_half = int((pager_count - 1) / 2)

    @property
    def start(self):
        return (self.current_page - 1) * self.per_page_num

    @property
    def end(self):
        return self.current_page * self.per_page_num

    def page_html(self):
        # 如果总页码 < 11个：
        if self.all_pager <= self.pager_count:
            pager_start = 1
            pager_end = self.all_pager + 1
        # 总页码  > 11
        else:
            # 当前页如果<=页面上最多显示11/2个页码
            if self.current_page <= self.pager_count_half:
                pager_start = 1
                pager_end = self.pager_count + 1

            # 当前页大于5
            else:
                # 页码翻到最后
                if (self.current_page + self.pager_count_half) > self.all_pager:
                    pager_end = self.all_pager + 1
                    pager_start = self.all_pager - self.pager_count + 1
                else:
                    pager_start = self.current_page - self.pager_count_half
                    pager_end = self.current_page + self.pager_count_half + 1

        page_html_list = []
        # 添加前面的nav和ul标签
        page_html_list.append('''
                    <nav aria-label='Page navigation>'
                    <ul class='pagination'>
                ''')
        first_page = '<li><a href="?page=%s">首页</a></li>' % (1)
        page_html_list.append(first_page)

        if self.current_page <= 1:
            prev_page = '<li class="disabled"><a href="#">上一页</a></li>'
        else:
            prev_page = '<li><a href="?page=%s">上一页</a></li>' % (self.current_page - 1,)

        page_html_list.append(prev_page)

        for i in range(pager_start, pager_end):
            if i == self.current_page:
                temp = '<li class="active"><a href="?page=%s">%s</a></li>' % (i, i,)
            else:
                temp = '<li><a href="?page=%s">%s</a></li>' % (i, i,)
            page_html_list.append(temp)

        if self.current_page >= self.all_pager:
            next_page = '<li class="disabled"><a href="#">下一页</a></li>'
        else:
            next_page = '<li><a href="?page=%s">下一页</a></li>' % (self.current_page + 1,)
        page_html_list.append(next_page)

        last_page = '<li><a href="?page=%s">尾页</a></li>' % (self.all_pager,)
        page_html_list.append(last_page)
        # 尾部添加标签
        page_html_list.append('''
                                           </nav>
                                           </ul>
                                       ''')
        return ''.join(page_html_list)

后端

 from app01.utils.mypage import Pagination
使用封装好的分页器代
def login(request):
    book_queryset = models.Book.objects.all()
    current_page = request.GET.get('page',1)
    all_count = book_queryset.count()
	1.实例化产生对象
	page_obj = Pagination(current_page=current_page,all_count=all_count)
	2.对真实数据进行切片操作
	page_queryset = book_queryset[page_obj.start:page_obj.end]
	return render(request,'login.html',locals())

前端

{% for book_obj in page_queryset %}
	<p>{{ book_obj.title }}</p>
{% endfor %}
{{ page_obj.page_html|safe }}

自定义分页器的分析过程

views后端

queryset对象支持切片取值
def index(request):
    # 1.获取用户想要访问的页码数
    current_page = request.GET.get('page',1)  # 如果没有page参数 默认就展示第一页
    # 转成整型
    current_page = int(current_page)
    # 2.每页展示10条数据
    per_page_num = 10

    # 3.定义起始位置和终止位置
    start_page = (current_page - 1) * per_page_num
    end_page = current_page * per_page_num

    # 4.统计数据的总条数
    book_queryset = models.Book.objects.all()
    all_count = book_queryset.count()

    # 5.求数据到底需要多少页才能展示完
    page_num, more = divmod(all_count,per_page_num)  # divmod(100,10)
    if more:
        page_num += 1
    # page_num就觉得了 需要多少个页码
    page_html = ''
    xxx = current_page  # xxx就是用户点击的数字
    if current_page < 6:
         current_page = 6
    for i in range(current_page-5,current_page+6):
        if xxx == i:
            page_html += '<li class="active"><a href="?page=%s">%s</a></li>'%(i,i)
        else:
            page_html += '<li><a href="?page=%s">%s</a></li>' % (i, i)

    book_queryset = book_queryset[start_page:end_page]
    return render(request,'index.html',locals())

html前端

<table class="table table-hover table-bordered">
    <thead>
    <tr>
        <th>id</th>
        <th>书名</th>
        <th>详情</th>
        <th>操作</th>
    </tr>
    </thead>
    <tbody>
    {% for page in book_querset %}
        <tr>
            <td>{{ forloop.counter }}</td>
            <td>{{ page.title }}</td>
            <td>{{ page.addr }}</td>
            <td>
                <a href="">添加</a>
                <a href="">删除</a>
            </td>
        </tr>

    {% endfor %}
    </tbody>
</table>
<nav aria-label="Page navigation">
  <ul class="pagination">
    <li>
      <a href="#" aria-label="Previous">
        <span aria-hidden="true">&laquo;</span>
      </a>
    </li>
      {{ page_html|safe }}
    <li>
      <a href="#" aria-label="Next">
        <span aria-hidden="true">&raquo;</span>
      </a>
    </li>
  </ul>
</nav>

数据模型定义（批量操作数据）

from django.db import models
# Create your models here.
class Test(models.Model):
    name = models.CharField(max_length=32, null=True, default=None)
    age = models.IntegerField(max_length=32, null=True, default=None)

在urls.py文件添加一个路径

urlpatterns = [
    path('admin/', admin.site.urls),
    path("favicon.ico", RedirectView.as_view(url='static/favicon.ico')),
    re_path('^index/',views.index),
]

在views.py添加数据

批量添加单个字段

def index(request):
    product_list_to_insert = list()
	for i in range(1000):
        product_list_to_insert.append(models.Test(name='123'))
    models.Test.objects.bulk_create(product_list_to_insert) 

批量添加多个字段

# ############### 添加数据 ###############    
def index(request):
    import random

    product_list_to_insert = list()
    for x in range(100):
       #注意下面的添加方式 product_list_to_insert.append(models.Test(name='apollo' + str(x), age=random.randint(18, 89)))
    models.Test.objects.bulk_create(product_list_to_insert)
    return render(request, 'index.html')

批量更新数据

批量更新数据时，先进行数据过滤，然后再调用update方法进行一次性地更新。下面的语句将生成类似update....frrom....的SQL语句。
# ############### 更新数据 ###############
Test.objects.filter(name__contains='apollo1').update(name='Jack')

批量删除数据

批量更新数据时，先是进行数据过滤，然后再调用delete方法进行一次性删除。
下面的语句讲生成类似delete from ... where ... 的SQL语句。
# ############### 删除数据 ###############
Test.objects.filter(name__contains='jack').delete()

创建多对多表关系的三种方式

方式1：全自动创建（推荐使用**）

优点：好处在于 django orm会自动帮你创建第三张关系表
缺点：但是它只会帮你创建两个表的关系字段（俩个book_id,author_id） 不会再额外添加字段
虽然方便 但是第三张表的扩展性较差 无法随意的添加额外的字段

class Book(models.Model):
    ...
    authors = models.ManyToManyField(to='Author')

class Author(models.Models):
	...

方式2：纯手动（不推荐使用）

自己手动添加外键

优点：好处在于第三张表是可以任意的添加额外的字段

缺点：不足之处是在于orm查询的时候，很多方法不支持，查询的时候非常的麻烦

class Book(models.Model):
                ...
                
class Author(models.Models):
	...
            
class Book2Author(models.Model):
	book_id = models.ForeignKey(to='Book')
	author_id = models.ForeignKey(to='Author')
	create_time = models.DateField(auto_now_add=True)

方式3半自动(推荐使用，扩展性高)

3.半自动(推荐使用******)
手动建表 但是你会告诉orm 第三张表是你自己建的
orm只需要给我提供方便的查询方法
第三种虽然可以使用orm查询方法，但是不支持使用下面的方法：
add()
set()
remove()
clear()

class Book(models.Model):
    ...
    authors = models.ManyToManyField(to='Author', through='Book2Author', through_fields=('book','author'))#告诉django,是和那个表多对多关联，关联表是什么，关联的字段是什么
class Author(models.Model):
    ...
    #books = models.ManyToManyField(to='Book', through='Book2Author', through_fields=('author', 'book'))
class Book2Author(models.Model):
    book = models.ForeignKey(to='Book')
    author = models.ForeignKey(to='Author')
    create_time = models.DateField(auto_now_add=True)#建立额外的字段

注意

1. 半自动 一定要加两个额外的参数： through='Book2Author', through_fields=('book','author')
2. 后面字段的顺序：由第三张表通过哪个字段查询单表 就把哪个字段放前面
3. 在设计项目的时候 一定要给自己留后路 防止后续的迭代更新 ，因此推荐使用方法3

Django的内置分页器（paginator）简介

在页面显示分页数据，需要用到Django分页器组件

from django.core.paginator import Paginator

Paginator对象：    paginator = Paginator(user_list, 10)
# per_page: 每页显示条目数量
# count:    数据总个数
# num_pages:总页数
# page_range:总页数的索引范围，如: (1,10),(1,200)
# page:     page对象    
page对象：page=paginator.page(1)
# has_next              是否有下一页
# next_page_number      下一页页码
# has_previous          是否有上一页
# previous_page_number  上一页页码
# object_list           分页之后的数据列表
# number                当前页
# paginator             paginator对象

应用View层

from django.shortcuts import render,HttpResponse

# Create your views here.
from app01.models import *
from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger

def index(request):

    '''
    批量导入数据:

    Booklist=[]
    for i in range(100):
        Booklist.append(Book(title="book"+str(i),price=30+i*i))
    Book.objects.bulk_create(Booklist)
    '''

    '''
分页器的使用:

    book_list=Book.objects.all()

    paginator = Paginator(book_list, 10)

    print("count:",paginator.count)           #数据总数
    print("num_pages",paginator.num_pages)    #总页数
    print("page_range",paginator.page_range)  #页码的列表



    page1=paginator.page(1) #第1页的page对象
    for i in page1:         #遍历第1页的所有数据对象
        print(i)

    print(page1.object_list) #第1页的所有数据


    page2=paginator.page(2)

    print(page2.has_next())            #是否有下一页
    print(page2.next_page_number())    #下一页的页码
    print(page2.has_previous())        #是否有上一页
    print(page2.previous_page_number()) #上一页的页码



    # 抛错
    #page=paginator.page(12)   # error:EmptyPage

    #page=paginator.page("z")   # error:PageNotAnInteger

    '''


    book_list=Book.objects.all()

    paginator = Paginator(book_list, 10)
    page = request.GET.get('page',1)
    currentPage=int(page)


    try:
        print(page)
        book_list = paginator.page(page)
    except PageNotAnInteger:
        book_list = paginator.page(1)
    except EmptyPage:
        book_list = paginator.page(paginator.num_pages)


    return render(request,"index.html",{"book_list":book_list,"paginator":paginator,"currentPage":currentPage})

模版层 index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css" 
    integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous">
</head>
<body>

<div class="container">

    <h4>分页器</h4>
    <ul>

        {% for book in book_list %}
             <li>{{ book.title }} -----{{ book.price }}</li>
        {% endfor %}

     </ul>


    <ul class="pagination" id="pager">

                 {% if book_list.has_previous %}
                    <li class="previous"><a href="/index/?page={{ book_list.previous_page_number }}">上一页</a></li>
                 {% else %}
                    <li class="previous disabled"><a href="#">上一页</a></li>
                 {% endif %}


                 {% for num in paginator.page_range %}

                     {% if num == currentPage %}
                       <li class="item active"><a href="/index/?page={{ num }}">{{ num }}</a></li>
                     {% else %}
                       <li class="item"><a href="/index/?page={{ num }}">{{ num }}</a></li>

                     {% endif %}
                 {% endfor %}



                 {% if book_list.has_next %}
                    <li class="next"><a href="/index/?page={{ book_list.next_page_number }}">下一页</a></li>
                 {% else %}
                    <li class="next disabled"><a href="#">下一页</a></li>
                 {% endif %}

            </ul>
</div>



</body>
</html>

扩展(可看)

'''
    显示左5，右5，总共11个页，
    1 如果总页码大于11
        1.1 if 当前页码减5小于1，要生成1到12的列表（顾头不顾尾，共11个页码）
            page_range=range(1,12)
        1.2 elif 当前页码+5大于总页码，生成当前页码减10，到当前页码加1的列表（顾头不顾尾，共11个页码）
            page_range=range(paginator.num_pages-10,paginator.num_pages+1)
        1.3 else 生成当前页码-5，到当前页码+6的列表
            page_range=range(current_page_num-5,current_page_num+6)
    2 其它情况，生成的列表就是pageinator的page_range
        page_range=paginator.page_range

    '''

def index(request):


    book_list=Book.objects.all()

    paginator = Paginator(book_list, 15)
    page = request.GET.get('page',1)
    currentPage=int(page)

    #  如果页数十分多时，换另外一种显示方式
    if paginator.num_pages>11:

        if currentPage-5<1:
            pageRange=range(1,11)
        elif currentPage+5>paginator.num_pages:
            pageRange=range(currentPage-5,paginator.num_pages+1)

        else:
            pageRange=range(currentPage-5,currentPage+5)

    else:
        pageRange=paginator.page_range


    try:
        print(page)
        book_list = paginator.page(page)
    except PageNotAnInteger:
        book_list = paginator.page(1)
    except EmptyPage:
        book_list = paginator.page(paginator.num_pages)


    return render(request,"index.html",locals())

def page_test(request):
    # book_list=[]
    # for i in range(100):
    #     book=Book(name='book%s'%i,price=10+i,pub_date='2018-09-18',publish_id=1)
    #     book_list.append(book)
    # Book.objects.bulk_create(book_list,10)
    book_list=Book.objects.all()
    # 生成paginator对象，传入书籍列表，每页10条数据
    paginator=Paginator(book_list,3)
    # 总页码数
    print(paginator.num_pages)
    # 页码列表
    print(paginator.page_range)
    # 总数据
    print(paginator.count)
    # 获取页面传来的页码
    current_page=int(request.GET.get('page',1))
    page_range=[]
    # 左5 右5

    # 获取页面传来的页码的page对象
    try:
        page=paginator.page(current_page)
        # print(page.has_next())            #是否有下一页
        # print(page.next_page_number())    #下一页的页码
        # print(page.has_previous())        #是否有上一页
        # print(page.previous_page_number()) #上一页的页码
        # 循环打印出当页对象
        for i in page:
            print(i)
    except Exception as e:
        current_page=1
        page = paginator.page(1)
    if paginator.num_pages>11:
        if current_page+5>paginator.num_pages:
            page_range=range(paginator.num_pages-10,paginator.num_pages+1)
        elif current_page-5<1:
            page_range=range(1,12)
        else:
            page_range=range(current_page-5,current_page+6)
    else:
        page_range=paginator.page_range

    return render(request,'page_test.html',locals())

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <link rel="stylesheet" href="/static/bootstrap-3.3.7-dist/css/bootstrap.min.css">
    <title>Title</title>
</head>
<body>

<ul>

    {% for foo in page %}
        <li>{{ foo.name }}</li>

    {% endfor %}

</ul>
<nav aria-label="Page navigation">
    <ul class="pagination">
        {% if page.has_previous %}
            <li>
                <a href="/page_test/?page={{ page.previous_page_number }}" aria-label="Previous">
                    <span aria-hidden="true">上一页</span>
                </a>
            </li>
        {% else %}
            <li class="disabled">
                <a href="#" aria-label="Previous">
                    <span aria-hidden="true">上一页</span>
                </a>
            </li>
        {% endif %}

        {% for foo in page_range %}
            {% if current_page == foo %}
                <li class="active"><a href="/page_test/?page={{ foo }}">{{ foo }}</a></li>
            {% else %}
                <li><a href="/page_test/?page={{ foo }}">{{ foo }}</a></li>
            {% endif %}

        {% endfor %}
        {% if page.has_next %}
            <li>
                <a href="/page_test/?page={{ page.next_page_number }}" aria-label="Next">
                    <span aria-hidden="true">下一页</span>
                </a>
            </li>
        {% else %}
            <li class="disabled">
                <a href="#" aria-label="Next">
                    <span aria-hidden="true">下一页</span>
                </a>
            </li>

        {% endif %}

    </ul>
</nav>


</body>
</html>