Question

I understand the basic try: except: finally: syntax for pythons error handling. What I don’t understand is how to find the proper error names to make readable code.

For example:

try:
     s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     s.connect((HOST, PORT))
     s.settimeout(60)               
     char = s.recv(1)

except socket.timeout:
    pass

so if socket raises a timeout, the error is caught. How about if I am looking for a connection refused. I know the error number is 10061. Where in the documentation do I look to find a meaning full name such as timeout. Would there be a similar place to look for other python modules? I know this is a newbie question but I have been putting in error handling my my code for some time now, without actually knowing where to look for error descriptions and names.

EDIT:

Thanks for all your responses.

would

except socket.error, exception:
    if exception.errno == ETIMEDOUT:
         pass

achieve the same result as

except socket.timeout:
    pass

Answer 1

To achieve what you want, you’ll have to grab the raised exception, extract the error code stored into, and make some if comparisons against errno codes:

try:
     s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     s.connect((HOST, PORT))
     s.settimeout(60)               
     char = s.recv(1)
except socket.error, exception:
    if exception.errno == errno.ECONNREFUSED:
        # this is a connection refused
    # or in a more pythonic way to handle many errors:
    {
       errno.ECONNREFUSED : manage_connection_refused,
       errno.EHOSTDOWN : manage_host_down,
       #all the errors you want to catch
    }.get(exception.errno, default_behaviour)()
except socket.timeout:
    pass

with :

def manage_connection_refused():
   print "Connection refused"

def manage_host_down():
   print "Host down"

def default_behaviour():
   print "error"