自定义分页

class Page(object):
    """
    这是我带上海全栈一期写的一个自定义分页类
    可以实现Django ORM数据的分页展示

    使用说明：
        from utils import mypage
        page_obj = mypage.Page(total_num, current_page, ‘publisher_list‘)
        publisher_list = data[page_obj.data_start:page_obj.data_end]
        page_html = page_obj.page_html()

        为了显示效果，show_page_num最好使用奇数

    """

    def __init__(self, total_num, current_page, url_prefix, per_page=10, show_page_num=11):
        """

        :param total_num: 数据的总条数
        :param current_page: 当前访问的页码
        :param url_prefix: 分页代码里a标签的前缀
        :param per_page: 每一页显示多少条数据
        :param show_page_num: 页面上最多显示多少个页码
        """
        self.total_num = total_num
        self.url_prefix = url_prefix

        self.per_page = per_page
        self.show_page_num = show_page_num

        # 通过初始化传入的值计算得到的值
        self.half_show_page_num = self.show_page_num // 2
        # 当前数据总共需要多少页码
        total_page, more = divmod(self.total_num, self.per_page)
        # 如果有余数，就把页码数+1
        if more:
            total_page += 1
        self.total_page = total_page
        # 对传进来的当前页码数做有效性校验
        try:
            current_page = int(current_page)
        except Exception as e:
            current_page = 1
        # 如果当前页码数大于总页码数，默认展示最后一页的数据
        # current_page = total_page if current_page > total_page else current_page
        if current_page > self.total_page:
            current_page = self.total_page
        # 如果当前页码数小于1，默认展示第一页的数据
        if current_page < 1:
            current_page = 1

        self.current_page = current_page

        # 求 页面上 需要展示的页码范围
        if self.current_page - self.half_show_page_num <= 1:
            page_start = 1
            page_end = show_page_num
        elif self.current_page + self.half_show_page_num >= self.total_page:
            page_end = self.total_page
            page_start = self.total_page - self.show_page_num + 1
        else:
            page_start = self.current_page - self.half_show_page_num
            page_end = self.current_page + self.half_show_page_num

        self.page_start = page_start
        self.page_end = page_end  # 我上面一通计算得到的页面显示的页码结束
        # 如果你一通计算的得到的页码数比我总共的页码数还多，我就把页码结束指定成我总共有的页码数
        if self.page_end > self.total_page:
            self.page_end = self.total_page

    @property
    def data_start(self):
        # 返回当前页应该从哪儿开始切数据
        return (self.current_page - 1) * self.per_page

    @property
    def data_end(self):
        # 返回当前页应该切到哪里为止
        return self.current_page * self.per_page

    def page_html(self):
        li_list = []
        # 添加前面的nav和ul标签
        li_list.append("""
            <nav aria-label="Page navigation">
            <ul class="pagination">
        """)

        if ‘?‘ in self.url_prefix:
            index = self.url_prefix.find(‘&page=‘)
            if not index == -1:
                self.url_prefix = self.url_prefix[0:index]
            href = "{0}&".format(self.url_prefix)
        else:
            href = "{0}?".format(self.url_prefix)

        # 添加首页
        li_list.append(‘<li><a href="{}page=1">首页</a></li>‘.format(href))
        # 添加上一页
        if self.current_page <= 1:  # 没有上一页
            prev_html = ‘<li class="disabled"><a aria-label="Previous"><span aria-hidden="true">&laquo;</span></a></li>‘
        else:
            prev_html = ‘<li><a href="{}page={}" aria-label="Previous"><span aria-hidden="true">&laquo;</span></a></li>‘.format(
                href,
                self.current_page - 1)
        li_list.append(prev_html)

        for i in range(self.page_start, self.page_end + 1):
            if i == self.current_page:
                tmp = ‘<li class="active"><a href="{0}page={1}">{1}</a></li>‘.format(href, i)
            else:
                tmp = ‘<li><a href="{0}page={1}">{1}</a></li>‘.format(href, i)
            li_list.append(tmp)
        # 添加下一页
        if self.current_page >= self.total_page:  # 表示没有下一页
            next_html = ‘<li class="disabled"><a aria-label="Previous"><span aria-hidden="true">&raquo;</span></a></li>‘
        else:
            next_html = ‘<li><a href="{}page={}" aria-label="Previous"><span aria-hidden="true">&raquo;</span></a></li>‘.format(
                href, self.current_page + 1)
        li_list.append(next_html)
        # 添加尾页
        li_list.append(‘<li><a href="{}page={}">尾页</a></li>‘.format(href, self.total_page))

        # 添加nav和ul的结尾
        li_list.append("""
            </ul>
        </nav>
        """)
        # 将生成的li标签 拼接成一个大的字符串
        page_html = "".join(li_list)
        return page_html