分页器,序列化组件,bulk_create,choices字段

分页器

<!--前端-->
{% for book in page_queryset %}
<p>{{ book.title }}</p>
{% endfor %}
{{ page_obj.page_html|safe }}

# 后端
book_list = models.Book.objects.all()
current_page = request.GET.get("page",1)
all_count = book_list.count()
page_obj = Pagination(current_page=current_page,all_count=all_count,per_page_num=10,pager_count=5)
page_queryset = book_list[page_obj.start:page_obj.end]

分页器模板代码

class Pagination(object):
    def __init__(self, current_page, all_count, per_page_num=2, 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)

from app01.utils.mypage import Pagination
def book(request):
    book_list = models.Book.objects.all()
    current_page = request.GET.get("page",1)
    all_count = book_list.count()
    page_obj = Pagination(current_page=current_page,all_count=all_count,per_page_num=10)
    page_queryset = book_list[page_obj.start:page_obj.end]


    return render(request,'booklist.html',locals())

<body>
<div class="container">
    <div class="row">
        <div class="col-md-8 col-md-offset-2">
            {% for book in page_queryset %}
            <p>{{ book.title }}</p>
            {% endfor %}
            {{ page_obj.page_html|safe }}
        </div>
    </div>
</div>
</body>

Django 序列化组件

什么时候用

后端想直接将实例化出来的数据对象直接发送给客户端，那么这个时候，就可以用Django给我们提供的序列化方式

# 后端:
def ser(request):
    #拿到用户表里面的所有的用户对象
    user_list=models.User.objects.all()
    #导入内置序列化模块
    from django.core import serializers
    #调用该模块下的方法，第一个参数是你想以什么样的方式序列化你的数据
    ret=serializers.serialize('json',user_list)
    return render(request,'index.html',locals())
​
# 前端得到: 
[{"model": "app01.user","pk": 1,"fields": 
  {"username": "jason","age": 18,"gender": 1}
    }......]

 

bulk_create 批量插入数据(高效)

l = []
for i in range(10000):
    l.append(models.Book2(name='第%s本书'%i))
models.Book2.objects.bulk_create(l)  # 批量插入数据 

choices字段参数

为什么用

1.对于类型性别,假否,婚否的字段,有固定字段数据的字段可以用choices参数
2.节省空间,因为存的是数字

如何使用

# models.py文件中:
class User(models.Model):
    username = models.CharField(max_length=32)
    age = models.IntegerField()
    choices = (
        (1,'男'),(2,'女'),(3,'其他')
    )
    gender = models.IntegerField(choices=choices)  # 指定choices参数
​
    """
    1 存choice里面罗列的数字与中文对应关系
         print(user_obj.get_gender_display())
            只要是choices字段 在获取数字对应的注释 固定语法
            get_字段名_display()
​
    2 存没有罗列出来的数字
        不会报错 还是展示数字
    """

# views.py文件中
def userlist(request):
    user_obj = models.User.objects.filter(pk=1).first()
    gender = user_obj.get_gender_display()  # 得到对应的性别注释,如'男'