how to get a return value from an exception ?

[Alex Martelli]

Shagshag13 wrote:

> hello,
> 
> i need to raise an exception which "carry" some data... i think that it's
> something like :
> 
> class MyException(Exception):
> 
>  def __init__(self, *args):
>   Exception.__init__(self, args)

This method __init__ is useless.  Just write:

class MyException(Exception): pass

for clarity and brevity.


>>>> raise MyException('one', 2, 'three')
> Traceback (most recent call last):
>   File "<pyshell#66>", line 1, in ?
>     raise MyException('one', 2, 'three')
> MyException: ('one', 2, 'three')
> 
> but them how to access to 'one', 2, and 'three' ?

try: raise MyException('one', 2, 'three')
except MyException, e:
    print repr(e.args)

e.args is the tuple ('one', 2, 'three') .


> it's ok if i do it like in "dive in python"
> 
>>>> class MyError(Exception):
> def __init__(self, value):
>     self.value = value
> def __str__(self):
>     return `self.value`
> 
> but here what does the `` stand for ?

A weird ancient way of spelling repr(self.value)
that some Pythonistas like (me, I don't).


Alex