2019.03.22 Django事物

Django中的事务处理

出现错误，要保证事务可以进行回滚

给我讲了事务的四大特性 ACID

• Django中的事务是自动提交模式

# -*- coding: utf-8 -*-
from __future__ import unicode_literals
​
from django.db import models
​
# Create your models here.
​
class Clazz(models.Model):
    cno = models.AutoField(primary_key=True)
    cname = models.CharField(max_length=30)
​
    class Meta:
        db_table='t_cls'
​
    def __unicode__(self):
        return u'Clazz:%s,%s'%(self.cno,self.cname)
​
class Stu(models.Model):
    sno = models.AutoField(primary_key=True)
    sname = models.CharField(max_length=30)
    score = models.PositiveIntegerField(max_length=3)
    created = models.DateField(auto_now_add=True)
    clazz = models.ForeignKey(Clazz,on_delete=models.CASCADE)
​
    from django.db.transaction import atomic
​
    @atomic
    def save(self, force_insert=False, force_update=False, using=None,
             update_fields=None):
        try:
            self.clazz = Clazz.objects.get(cname=self.clazz.cname)
        except Clazz.DoesNotExist:
            self.clazz = Clazz.objects.create(cname=self.clazz.cname)
            
        #制造异常
        1/0
​
        models.Model.save(self, force_insert, force_update, using,update_fields)
​
​
    class Meta:
        db_table='t_stu'
​
    def __unicode__(self):
        return u'Stu:%s,%s'%(self.sname,self.score)
​
​
​
​

#两张表中都没有插入新数据

from student.models import *
stu = Stu(sname='xiaowang',score=88,clazz=Clazz(cname='Oracle'))
stu.save()

Traceback (most recent call last):
File "<input>", line 1, in <module>
File "C:\Python27\lib\site-packages\django\utils\decorators.py", line 185, in inner
return func(*args, **kwargs)
File "D:\pythoncodes\django_20180402\demo\demo3\student\models.py", line 34, in save
1/0
ZeroDivisionError: integer division or modulo by zero

测试结果

装饰器的功能

• 将被装饰的函数当作参数传递给与装饰器对应的函数（名称相同的函数),并返回包装后的被装饰的函数

• 被修饰器修饰的函数具有相同特定的功能

二阶装饰器

​
def a(func):
    def _wrapper(*args,**kwargs):
        content = func(*args,**kwargs)
        return '<b>%s</b>'%content
    return _wrapper
@a
def b():
    return 'hello world'
    
b()
'<b>hello world</b>'
​
​

三阶装饰器

def a(bold=True):
    def _wrapper(func):
        def __wrapper(*args,**kwargs):
            content = func(*args,**kwargs)
            if bold:
                return '<b>%s</b>'%content
            else:
                return '<i>%s</i>'%content
        return __wrapper
    return _wrapper
    
                
@a(bold=False)
def b():
    return 'hello world'
    
    
b()
'<i>hello world</i>'
​
​