day75-<项目>-obj.get_XX_display()，分页的实现

def practice_page(request):
    users = [{'username': 'leon{}'.format(i),
              'password': 'pwd{}'.format(i)} for i in range(0, 301)]

    try:
        request_page_num = int(request.GET.get('page', 1))  # 获取请求页
        if request_page_num <= 0:
            request_page_num = 1
    except Exception as e:
        print('{}:分页请求参数非法！'.format(str(e)))
        request_page_num = 1
    request_page_num = int(request_page_num)  # 转化为 int 类型
    all_data_length = len(users)  # 总数据量
    each_page_show_number = 10  # 每页显示 10 条数据吧
    all_count_pages_number, more_page = divmod(all_data_length, each_page_show_number)
    if more_page:  # 如果有余数的话
        all_count_pages_number += 1
    max_show_page = 11  # 定义最大显示的数量数 11 页

    half_page = max_show_page // 2  # 获取中间页码
    if all_count_pages_number <= max_show_page:  # 如果我的总的页数加起来还不满 11 格
        start_page = 1  # 起始页写死为 1
        end_page = all_count_pages_number  # 最后一页同样写死
    else:
        if request_page_num - half_page <= 0:  # start开始出现 0 了
            start_page = 1  # 卡死第一页是 1
            end_page = max_show_page  # 最后一页是 最大允许显示的页数
        elif request_page_num + half_page >= all_count_pages_number:  # 如果已经最大了
            start_page = all_count_pages_number - max_show_page + 1
            end_page = all_count_pages_number
        else:
            start_page = request_page_num - half_page  # 定义开始的页码
            end_page = request_page_num + half_page  # 定义结束的页码

    html_list = []  # 定义一个空的列表
    first_li = '<li><a href="/crm/practice_page/?page=1">首页</a></li>'  # 首页
    html_list.append(first_li)  # 添加首页
    if request_page_num == 1:  # 请求页(当前页)为第一页的话
        pre_li = '<li class="disabled"><a href="#"><<</a></li>'
    else:
        pre_li = '<li><a href="/crm/practice_page/?page={}"><<</a></li>'.format(request_page_num - 1)
    html_list.append(pre_li)
    for num in range(start_page, end_page + 1):
        if request_page_num == num:  # 增加active样式
            li_html = '<li class="active"><a href="/crm/practice_page/?page={0}">{0}</a></li>'.format(num)
        else:
            li_html = '<li><a href="/crm/practice_page/?page={0}">{0}</a></li>'.format(num)
        html_list.append(li_html)  # 添加下一页
    if request_page_num == all_count_pages_number:  # 如果已经是请求的最后一页
        next_li = '<li class="disabled"><a href="#">>></a></li>'
    else:
        next_li = '<li><a href="/crm/practice_page/?page={}">>></a></li>'.format(request_page_num + 1)
    html_list.append(next_li)
    last_li = '<li><a href="/crm/practice_page/?page={}">尾页</a></li>'.format(all_count_pages_number)
    html_list.append(last_li)  # 添加尾页
    html_str = mark_safe(''.join(html_list))

    '''
    切片请求数量
    页数  从         到
    1    0           9
    2    10          19
    n    (n-1)*10    
    '''
    each_page_start_number = (request_page_num - 1) * each_page_show_number
    each_page_end_number = request_page_num * each_page_show_number

    return render(request,
                  'crm/practice_page.html',
                  {'users': users[each_page_start_number:each_page_end_number],
                   # 'pages': range(start_page, end_page + 1),
                   'html_str': html_str})

"""
分页器
"""
from django.utils.safestring import mark_safe


class Pagination:
    def __init__(self, request, all_data_length, each_page_show_number=10, max_show_page=11):
        """
        :param request:
        :param all_data_length: 数据的总长度
        :param each_page_show_number: 每一页需要展示多少条数据，默认 10 条
        :param max_show_page: 最大显示多少页
        """
        self.url = request.path_info
        self.each_page_show_number = each_page_show_number
        try:
            self.request_page_num = int(request.GET.get('page', 1))  # 获取请求页
            if self.request_page_num <= 0:
                self.request_page_num = 1
        except Exception as e:
            print('{}:分页请求参数非法！'.format(str(e)))
            self.request_page_num = 1

        self.request_page_num = int(self.request_page_num)  # 转化为 int 类型

        self.all_count_pages_number, more_page = divmod(all_data_length, each_page_show_number)
        if more_page:  # 如果有余数的话
            self.all_count_pages_number += 1

        half_page = max_show_page // 2  # 获取中间页码
        if self.all_count_pages_number <= max_show_page:  # 如果我的总的页数加起来还不满 11 格
            self.start_page = 1  # 起始页写死为 1
            self.end_page = self.all_count_pages_number  # 最后一页同样写死
        else:
            if self.request_page_num - half_page <= 0:  # start开始出现 0 了
                self.start_page = 1  # 卡死第一页是 1
                self.end_page = max_show_page  # 最后一页是 最大允许显示的页数
            elif self.request_page_num + half_page >= self.all_count_pages_number:  # 如果已经最大了
                self.start_page = self.all_count_pages_number - max_show_page + 1
                self.end_page = self.all_count_pages_number
            else:
                self.start_page = self.request_page_num - half_page  # 定义开始的页码
                self.end_page = self.request_page_num + half_page  # 定义结束的页码

    @property
    def each_page_start_number(self):
        """
        :return:但会某一页的开头的信息序号
        """
        return (self.request_page_num - 1) * self.each_page_show_number

    @property
    def each_page_end_number(self):
        return self.request_page_num * self.each_page_show_number

    @property
    def html_str(self):
        html_list = []  # 定义一个空的列表
        first_li = '<li><a href="{}?page=1">首页</a></li>'.format(self.url)  # 首页
        html_list.append(first_li)  # 添加首页
        if self.request_page_num == 1:  # 请求页(当前页)为第一页的话
            pre_li = '<li class="disabled"><a href="#"><<</a></li>'
        else:
            pre_li = '<li><a href="{}?page={}"><<</a></li>'.format(self.url, self.request_page_num - 1)
        html_list.append(pre_li)
        for num in range(self.start_page, self.end_page + 1):
            if self.request_page_num == num:  # 增加active样式
                li_html = '<li class="active"><a href="{0}?page={1}">{1}</a></li>'.format(self.url, num)
            else:
                li_html = '<li><a href="{0}?page={1}">{1}</a></li>'.format(self.url, num)
            html_list.append(li_html)  # 添加下一页
        if self.request_page_num == self.all_count_pages_number:  # 如果已经是请求的最后一页
            next_li = '<li class="disabled"><a href="#">>></a></li>'
        else:
            next_li = '<li><a href="{}?page={}">>></a></li>'.format(self.url, self.request_page_num + 1)
        html_list.append(next_li)
        last_li = '<li><a href="{}?page={}">尾页</a></li>'.format(self.url, self.all_count_pages_number)
        html_list.append(last_li)  # 添加尾页
        html_str = mark_safe(''.join(html_list))
        return html_str