007 分页函数

class Pagination(object):
def init(self, current_page, all_count, per_page_num=10, 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

    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)