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)
# 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())
{% 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
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