Python异常处理 - 使用字符串消息引发的异常，不包括字符列表

Question

I am trying to raise and except a custom exception with a message, but the message string prints as tuple of characters. My error class:

class myError(Exception):
    def __init__(self, arg):
        self.args = arg

And try-raise-except part :

try:
    raise myError('some message.')
except myError, e:
    print e.args

This when raised properly, prints:`

('s', 'o', 'm', 'e', ' ', 'm', 'e', 's', 's', 'a', 'g', 'e', '.', ' ')

Of course, I wanted 'some message. '. What is going on?

Answer 1

You Don't need to declare __init__ in Your Exception:

>>> class myError(Exception):
...     pass

>>> raise myError('some message.')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
__main__.myError: some message.

Answer 2

Your problem is that args is already a member of Exception , and it is defined as:

args
The tuple of arguments given to the exception constructor

So you assign a tuple with an iterable (a string is an iterable of characters) and end with a tuple of characters.

How to fix:

1. just use args from Exception:

    class myError(Exception): pass try: raise myError('message') except myError as e: print(e.args[0]) 

2. use a new member name:

    class myError(Exception): def __init__(self, arg): self.msg = arg try: raise myError('message',) except myError as e: print(e.msg)