自定义分页

"""
分页组件使用示例：
    1) 先取出所有数据USER_LIST
    2) 实例化：
        obj = Pagination(request.GET.get('page',1), len(USER_LIST), request)
    3) 对所有数据列表切片（即切出一页数据）：
        page_user_list = USER_LIST[obj.start:obj.end]
    4) 返回给页面：
        return render(request,'index.html',{'users': page_user_list, 'obj': obj})
    5) 模板页面通过 {{ obj.page_html|safe }} 渲染页码
"""

class Pagination(object):

    # 第一步  初始化页面
    def __init__(self,current_page_num,all_count,request,per_page_num=5,pager_count=11):
        """
        封装分页相关数据
        :param current_page_num: 当前访问页的数字
        :param all_count:    分页数据中的数据总条数
        :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_num = int(current_page_num)
        except Exception as e:
            current_page_num = 1

        if current_page_num <1:
            current_page_num = 1

        self.current_page_num = current_page_num

        self.all_count = all_count
        self.per_page_num = per_page_num


        # 第二步  实际总页码
        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)  # 5


        # 保存搜索条件

        import copy
        self.params=copy.deepcopy(request.GET) # {"a":"1","b":"2"}

    @property  #属性方法  在外部views里 切片的时候不用加括号  直接调用 start就可以
    def start(self):
        return (self.current_page_num - 1) * self.per_page_num

    @property
    def end(self):
        return self.current_page_num * 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_num <= 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_num + self.pager_count_half) > self.all_pager:

                    pager_start = self.all_pager - self.pager_count + 1
                    pager_end = self.all_pager + 1

                else:
                    pager_start = self.current_page_num - self.pager_count_half
                    pager_end = self.current_page_num + self.pager_count_half + 1

        page_html_list = []

        first_page = '<li><a href="?page=%s">首页</a></li>' % (1,)
        page_html_list.append(first_page)

        if self.current_page_num <= 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_num - 1,)

        page_html_list.append(prev_page)


        #self.params=copy.deepcopy(request.GET) # {"a":"1","b":"2"}
        # 主要的for循环
        for i in range(pager_start, pager_end):

            self.params["page"]=i

            if i == self.current_page_num:
                temp = '<li class="active"><a href="?%s">%s</a></li>' %(self.params.urlencode(),i)
            else:
                temp = '<li><a href="?%s">%s</a></li>' % (self.params.urlencode(),i,)
            page_html_list.append(temp)



        if self.current_page_num >= 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_num + 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)

        return ''.join(page_html_list)