Is there a way beyond catching exceptions(HTTPError,URLError), to check if access to a url is permitted.
I have to constantly(every 30 secs) ping a url (using urllib2.open)(which might or might not be valid).
And throwing and catching exceptions each time seems excessive. I couldn't find anything in the documentation.
There's nothing wrong with using try/except.  That's the way to do such things in python.

it's easier to ask forgiveness than permission
Python: Checking if you can connect to a given url (urllib2)