自定义分页器使用/批量插入数据

多对多表的三种创建方式

1.全自动创建----ManyToManyField
  class Book(models.Model):
     title = models.CharField(max_length=32)
		 authors = models.ManyToManyField(to='Author')
  class Author(models.Model):
     name = models.CharField(max_length=32)
 
优势:自动创建第三张表 并可以这个表进行 add remove set clear四种操作
劣势:第三张表无法创建更多的字段 扩展性较差


2.纯手动创建

 class Book(models.Model):
        title = models.CharField(max_length=32)
 class Author(models.Model):
        name = models.CharField(max_length=32)

class Book2Author(models.Model):
        book = models.ForeignKey(to='Book')
        author = models.ForeignKey(to='Author')
        others = models.CharField(max_length=32)
        join_time = models.DateField(auto_now_add=True)
        
第三张表的外键分别是2个 关联的表格 
优势：第三张表完全自己创建 扩展性抢
劣势：编写繁杂 并不再支持add remove set clear四种操作 和 正反向查询方式



3.半自动创建
 class Book(models.Model):
        title = models.CharField(max_length=32)
        authors = models.ManyToManyField(to='Author', through='Book2Author',      									through_fields=('book','author')
# 在ManyToManyField中 关联表 through=第三张表名 through_fields('book','author')
                                   # 关联的第三张表字段
                                         
 class Author(models.Model):
        name = models.CharField(max_length=32)
    class Book2Author(models.Model):
        book = models.ForeignKey(to='Book', on_delete=models.CASCADE)
        author = models.ForeignKey(to='Author', on_delete=models.CASCADE)
        others = models.CharField(max_length=32)
        join_time = models.DateField(auto_now_add=True)
                                         
 优势:第三张表完全由自己创建 扩展性强 正反向概念依然清晰可用
 劣势:编写繁琐不再支持add、remove、set、clear                    

django内置序列化组建（drf）前身

'''前后端分离的项目 视图函数只需要返回json格式的数据即可'''
from app01 import models
from django.http import JsonResponse


def ab_ser_func(request):
    # 1.查询所有的书籍对象
    book_queryset = models.Book.objects.all()  # queryset [对象、对象]
    # 2.封装成大字典返回
    data_dict = {}
    for book_obj in book_queryset:
        temp_dict = {}
        temp_dict['pk'] = book_obj.pk
        temp_dict['title'] = book_obj.title
        temp_dict['price'] = book_obj.price
        temp_dict['info'] = book_obj.info
        data_dict[book_obj.pk] = temp_dict  # {1:{},2:{},3:{},4:{}}
    return JsonResponse(data_dict)
  
  
 普通写法

from django.core import serializers

导入内置模块
res = serializers.serialize('json', book_queryset)
# 直接把从数据库拿到的queryset 直接发送即可  模块会帮你转化为json格式
return HttpResponse(res)


前端就会直接接收到数据为 json格式的

批量插入数据

如果要批量对某个表插入数据 
使用关键词 bulk_create 批量创建
         bulk_update 批量更新

book_list = []
for i in range(10000):
  book_obj = models.Book(name='第%s本书'%i)
  book_list.append(book_obj)
  # 先创建所有对象 并汇集到一个列表 这时候还没有对数据库进行操作
  
models.Book.objects.bulk_create(book_list)
# 直接把所有对象列表放入bulk_create中即可

自定义分页器使用

当我们需要使用非django内置的第三方组建或代码时
统一在项目根目录下创建一个 utils文件夹 用于存放

class Pagination(object):
    def __init__(self, current_page, all_count, per_page_num=2, pager_count=11):
        """
        封装分页相关数据
        :param current_page: 当前页
        :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
        """
        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)

后端代码

from utils.mypage import Pagination
def book_list(request):
    book_obj_list = models.Book.objects.all()
    all_count = book_obj_list.count()
    current_page = request.GET.get('page',1)
    page_obj = Pagination(current_page=current_page,all_count=all_count)
    # 实例化传值生成对象
    page_obj_list = book_obj_list[page_obj.start:page_obj.end]
    # 对总数据进行切片处理
    return render(request, 'book_list.html', locals())
  
  
前端代码

   <div class="text-center">
    {{ page_obj.page_html|safe }}
    </div>