批量插入,分页器,django自带序列化组件

批量插入数据

当有需要大量插入/创造数据的需求时,原始插入方法耗时较长:

for i in range(1000):
    models.Book.objects.create(title = 'number %s' % i)
book_queryset = models.Book.objects.all()
return render(request, 'ab_plcr.html', local())

前端仅仅是取book_obj.title进行全部展示 

原方法耗时长,迟迟加载出来后才会展示页面

而使用bulk_create批量插入时,能大量减省操作时间,塞对象列表:

book_list = []
for i in range(10000):
    book_obj = models.Book(title='number %s ' % i) #创建10000个book对象
    book_list.append(book_obj)
models.Book.objects.bulk_create(book_list) #直接把要创建对象塞进去

 分页器

Django中有分页器模块,但使用起来复杂且功能简单。我们需要在掌握上面分页器推导思路下,创造自定义分页器来使用

自定义分页器代码已经封装好,直接使用即可↓:

# 分页器代码封装
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
        """
        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)
分页器
   # 获取参数值
   book_list = models.Book.objects.all()
   current_page = request.GET.get("page",1)
   all_count = book_list.count()
   # 传值生成对象
   page_obj = Pagination(current_page=current_page,all_count=all_count,per_page_num=10)
   # 对总数进行切片操作
   page_queryset = book_list[page_obj.start:page_obj.end]
   # 传递给前端
   return render(request,'booklist.html',locals())
后端调用
{% for book in page_queryset %}
    <p>{{ book.title }}</p>
    #应该是不要这行?<nav aria-label = "Page navigation"></nav>
{% endfor %}
{{ page_obj.page_html|safe }} # 转义
前端调用

django自带序列化组件

项目多采用前后端分离开发模式,保证数据多用性

后端通常将数据打包为[{}, {}, {}]的格式,然后序列化为json格式传递给前端

Django自带有序列化组件,比如简单的serializers

from django.core import serializers
user_queryset = models.User.objects.all()                # 拿到数据的querySet对象
res = serializers.serialize('json', user_querset)        # 第一个为想转换数据后的格式,第二个为待转数据
return HttpResponse(res)

利用serializers模块自动将数据变为json格式数据,并且非常全面

 

posted @ 2022-11-07 14:31  weer-wmq  阅读(42)  评论(0编辑  收藏  举报