newbie question about confusing exception handling in urllib

[cabbar at gmail.com]

Ah, looks better. 

But, 2 questions:

1. I should also catch ConnectionResetError I am guessing.
2. How do I handle all other exceptions, just say Exception: and handle them? I want to silently ignore them.

Thanks...

On Tuesday, April 9, 2013 2:41:51 PM UTC+3, cab... at gmail.com wrote:
> Hi,
> 
> 
> 
> I have been using Java/Perl professionally for many years and have been trying to learn python3 recently. As my first program, I tried writing a class for a small project, and I am having really hard time understanding exception handling in urllib and in python in general...
> 
> Basically, what I want to do is very simple, try to fetch something "tryurllib.request.urlopen(request)", and:
> 
>   - If request times out or connection is reset, re-try n times
> 
>   - If it fails, return an error
> 
>   - If it works return the content.
> 
> 
> 
> But, this simple requirement became a nightmare for me. I am really confused about how I should be checking this because:
> 
>   - When connection times out, I sometimes get URLException with "reason" field set to socket.timeout, and checking (isinstance(exception.reason, socket.timeout)) works fine
> 
>   - But sometimes I get socket.timeout exception directly, and it has no "reason" field, so above statement fails, since there is no reason field there.
> 
>   - Connection reset is a totally different exception
> 
>   - Not to mention, some exceptions have msg / reason / errno fields but some don't, so there is no way of knowing exception details unless you check them one by one. The only common thing I could was to find call __str__()?
> 
>   - Since, there are too many possible exceptions, you need to catch BaseException (I received URLError, socket.timeout, ConnectionRefusedError, ConnectionResetError, BadStatusLine, and none share a common parent). And, catching the top level exception is not a good thing.
> 
> 
> 
> So, I ended up writing the following, but from everything I know, this looks really ugly and wrong???
> 
> 
> 
>         try: 
> 
>             response = urllib.request.urlopen(request)
> 
>             content = response.read()
> 
>         except BaseException as ue:
> 
>             if (isinstance(ue, socket.timeout) or (hasattr(ue, "reason") and isinstance(ue.reason, socket.timeout)) or isinstance(ue, ConnectionResetError)):
> 
>                 print("REQUEST TIMED OUT")
> 
> 
> 
> or, something like:
> 
> 
> 
>         except:
> 
>             (a1,a2,a3) = sys.exc_info()
> 
>             errorString = a2.__str__()
> 
>             if ((errorString.find("Connection reset by peer") >= 0) or (errorString.find("error timed out") >= 0)):
> 
> 
> 
> Am I missing something here? I mean, is this really how I should be doing it?
> 
> 
> 
> Thanks.