How do I get info on an exception ?

[Bengt Richter]

On Thu, 17 Jul 2003 23:29:40 -0700, Erik Max Francis <max at alcyone.com> wrote:

>Frank wrote:
>
>> Using Python 2.2.2,
>> I want to catch all exceptions from "socket.gethostbyaddr(ip)"
>> 
>> From IDLE, I can generate:
>> >>> socket.gethostbyaddr('1.2')
>> Traceback (most recent call last):
>>   File "<pyshell#28>", line 1, in ?
>>     socket.gethostbyaddr('1.2')
>> herror: (11004, 'host not found')   <=== what I want when I catch
>> 
>> When I run this code:
>>         try:
>>             hostname, aliases, hostip = socket.gethostbyaddr(ip)
>>             return (hostip, hostname)
>>         except:
>>             print sys.exc_info()
>>             print sys.exc_type
>>             return
>
>Use the format:
>
>	try:
>	    ...
>	except ErrorType, e:
>	    ... do something with exception object e ...
>
Indeed. Or if you want to catch all standard exceptions until you know what is
happening, you could pick from the following. I guess you could also catch all
exceptions defined in a module without knowing what they're named, and re-raise
if other, e.g., with (untested!)

        if not repr(e.__class__).startswith('socket'): raise

is there another way to do that?

 >>> import socket
 >>> try:
 ...     socket.gethostbyaddr('1.2')
 ... except Exception, e:
...     print 'plain e:', e
...     print 'e class:', e.__class__
...     print 'e class name:', e.__class__.__name__
...     print 'vars keys:', vars(e).keys()
...     print 'vars dict:', vars(e)
...     print 'additional inherited clutter seen by dir:\n',dir(e)
...
plain e: (11004, 'host not found')
e class: socket.herror
e class name: herror
vars keys: ['args']
vars dict: {'args': (11004, 'host not found')}
additional inherited clutter seen by dir:
['__doc__', '__getitem__', '__init__', '__module__', '__str__', 'args']

You could also print a formatted vars(e) to see unanticipated attributes more nicely
with e.g., (untested!) print ''.join(['%16s = %r\n' %(k,v) for k,v in vars(e).items()])

>>>> import socket
>>>> socket.error
><class socket.error at 0x8154304>
>>>> try:
>...  socket.gethostbyaddr('1.2')
>... except socket.error, e:
>...  print e, dir(e), e.args
>... 
>(1, 'Unknown host') ['__doc__', '__getitem__', '__init__', '__module__',
>'__str__', 'args'] (1, 'Unknown host')
>
>> How do I get the "(11004, 'host not found')" part?
>> More importantly, where is the answer documented that I should
>> have looked?
>
>Check the part on exception handling.
>
Interactively, help('exceptions') is also helpful (note quotes)

Regards,
Bengt Richter