How can I figure whether to have e in "except urllib2.URLError, e"

Question

I got this code while I was looking into urllib2.

import urllib2
req = urllib2.Request('http://www.baibai.com')
try: urllib2.urlopen(req)
except urllib2.URLError,e: 
    print e.reason

I got confused when and whether to use e in the statement except urllib2.URLError, e: since it seems OK to use except urllib2.URLError: (without e).

Can every except statement have the format except:XXXX, e or just in some cases?

if you are not going to do something with the "e" then don't have it. Here you are printing e.reason, so it's useful. — Paul Collingwood, Jan 25 '15 at 13:48

score 4 · Accepted Answer · edited May 23 '17 at 12:12

Using the syntax urllib2.URLError, e you have access to the exception that was thrown (for example to print the message). If you only use except urllib2.URLError you indicate that you want to do something when a URLError is thrown, but you don't need the actual exception object.

Note that you are using a outdated python version because you are using , in your except blocks. Python 3+ requires as instead of , (except urllib2.URLError as e) while only Python 2.5- uses the , syntax.

I recommend you learn a bit about exceptions. Here's the official documentation on exceptions. More information about , vs as can be found on this StackOverflow answer.

How can I figure whether to have e in "except urllib2.URLError, e"

1 Answers1