Is it reasonable in Python to catch a generic exception, then use isinstance()
to detect the specific type of exception in order to handle it appropriately?
I'm playing around with the dnspython toolkit at the moment, which has a range of exceptions for things like a timeout, an NXDOMAIN response, etc. These exceptions are subclasses of dns.exception.DNSException
, so I am wondering if it's reasonable, or pythonic, to catch DNSException
then check for a specific exception with isinstance()
.
e.g.
try:
answers = dns.resolver.query(args.host)
except dns.exception.DNSException as e:
if isinstance(e, dns.resolver.NXDOMAIN):
print "No such domain %s" % args.host
elif isinstance(e, dns.resolver.Timeout):
print "Timed out while resolving %s" % args.host
else:
print "Unhandled exception"
I'm new to Python so be gentle!
That's what multiple except
clauses are for:
try:
answers = dns.resolver.query(args.host)
except dns.resolver.NXDOMAIN:
print "No such domain %s" % args.host
except dns.resolver.Timeout:
print "Timed out while resolving %s" % args.host
except dns.exception.DNSException:
print "Unhandled exception"
Be careful about the order of the clauses: The first matching clause will be taken, so move the check for the superclass to the end.