分页：pagination.py-526互联

'''
一、在视图函数中：
	def pretty_list(request):
		# 0.搜索数据
		data_dict = {}
		search_data = request.GET.get('q', '')
		if search_data:
			data_dict['mobile__contains'] = search_data
		# 1.根据情况筛选数据
		queryset = models.PrettyNum.objects.filter(**data_dict).order_by('-id')
		# 2.实例化分页对象
		page_object = Pagination(request, queryset,page_size=20)
		context = {
			'search_data': search_data,
			'queryset': page_object.page_queryset,  # 分完页的数据
			'page_string': page_object.html()  # 页码
		}
		return render(request, 'pretty_list.html', context)
二、在HTML中：
	<ul class="pagination">
		{{ page_string }}
	</ul>
'''
from django.utils.safestring import mark_safe

class Pagination(object):
	    def __init__(self, request, queryset, page_size=10, page_param='page', plus=5):
    '''
    :param request: 请求的对象
    :param queryset: 符合条件的数据，根据他进行分页
    :param page_size:每页显示多少条数据
    :param page_param:在URL中传递的分页的参数：/pretty/list/?page=page_param
    :param plus:显示当前面的前后几页。
    '''
    # 保存搜索条件
    import copy
    query_dict = copy.deepcopy(request.GET)
    query_dict._mutable = True
    self.query_dict = query_dict
    self.page_param = page_param

    page = request.GET.get(page_param, '1')
    if page.isdecimal():
        page = int(page)
    else:
        page = 1
    self.page = page
    self.page_size = page_size
    self.start = (page - 1) * page_size
    self.end = page * page_size

    self.page_queryset = queryset[self.start:self.end]

    # 数据库的总条数
    total_count = queryset.count()

    # 总页码
    total_page_count, div = divmod(total_count, page_size)
    if div:
        total_page_count += 1
    self.total_page_count = total_page_count
    self.plus = plus

	def html(self):
		# 计算出，显示当前页的前5页、后5页
		if self.total_page_count <= 2 * self.plus + 1:
			# 数据库中的数据比较少，都没有达到11页，
			start_page = 1
			end_page = self.total_page_count
		else:
			# 数据库中的数据比较多，大于11页

			# 当前页<5时
			if self.page <= self.plus:
				start_page = 1
				end_page = 2 * self.plus + 1
			else:
				# 当前>5时：当前页+5>总页面
				if (self.page + self.plus) > self.total_page_count:
					start_page = self.total_page_count - 2 * self.plus
					end_page = self.total_page_count
				else:
					start_page = self.page - self.plus
					end_page = self.page + self.plus

		# 页码
		page_str_list = []

		self.query_dict.setlist(self.page_param, [1])
		page_str_list.append('<li><a href="?{}">首页</a></li>'.format(self.query_dict.urlencode()))

		# 上一页
		if self.page > 1:
			self.query_dict.setlist(self.page_param, [self.page - 1])
			prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
		else:
			self.query_dict.setlist(self.page_param, [1])
			prev = '<li><a href="?{}">上一页</a></li>'.format(self.query_dict.urlencode())
		page_str_list.append(prev)

		for i in range(start_page, end_page + 1):
			self.query_dict.setlist(self.page_param, [i])
			if i == self.page:
				ele = '<li class="active"><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)
			else:
				ele = '<li><a href="?{}">{}</a></li>'.format(self.query_dict.urlencode(), i)

			page_str_list.append(ele)

		# 下一页
		if self.page < self.total_page_count:
			self.query_dict.setlist(self.page_param, [self.page + 1])
			prev = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
		else:
			self.query_dict.setlist(self.page_param, [self.total_page_count])
			prev = '<li><a href="?{}">下一页</a></li>'.format(self.query_dict.urlencode())
		page_str_list.append(prev)

		# 尾页
		self.query_dict.setlist(self.page_param, [self.total_page_count])
		page_str_list.append('<li><a href="?{}">尾页</a></li>'.format(self.query_dict.urlencode()))

		search_string = '''
				   <li>
					   <form action="" method="get" style="float:left;margin-left: -1px;">
						   <input name="page"
								  style="position: relative;float: left;display: inline-block;width: 88px;border-radius: 0;"
								  class="form-control" placeholder="页码">
						   <button style="border-radius: 0" class="btn btn-default" type="submit">跳转</button>
					   </form>
				   </li>
			   '''
		page_str_list.append(search_string)

		page_string = mark_safe(''.join(page_str_list))
		return page_string