python - 我在异常处理中有一个不同的异常？

Question

在最后一行中，当 i 使用别名打印消息时，它运行良好。例如

except insufficient as i :
    print("exception is caught",i.msg)

但是当我这样做的时候

except insufficient :
    print("exception is caught",insufficient.msg)

这是一个错误..为什么？？？

```class insufficient(ZeroDivisionError):
    def __init__(self,arg):
            self.msg=arg
balance=5000
w=int(input("enter a number"))
try:
    if w>5000:
        raise insufficient("balance in the account is insufficient")
    balance=balance-w
    print("no exception and balance is=",balance)
except insufficient :
    print("exception is caught",insufficient.msg)```

错误日志:-

Traceback (most recent call last):
  File "C:\Users\ahmod\AppData\Local\Programs\Python\Python37-32\hello.py", line 8, in <module>
    raise insufficient("balance in the account is insufficient")
insufficient: balance in the account is insufficient

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\ahmod\AppData\Local\Programs\Python\Python37-32\hello.py", line 12, in <module>
    print("exception is caught",insufficient.msg)
AttributeError: type object 'insufficient' has no attribute 'msg'

Answer 1

当你这样做时:

except insufficient as i:

try block 中的代码抛出的任何 Exception 都分配给变量 i 并在 中可用除了 block 。因此，如果您的 try block 抛出 insufficient 异常，那么该异常将分配给 i。因此你可以引用i.msg。

但由于 msg 是类 insufficient 中的对象属性，因此 insufficient.msg 的计算结果为空。

最后:

except insufficient:

不使抛出的对象在 except block 中可用。 insufficient 这里只是一个类型标识符。所以你不能访问 msg 属性。