I'm curious if there are best practices for handling exceptions raised by lower level modules and packages. For example, I wrote an application called polly[1] which constructs a personalized dictionary from email messages using IMAP4. That dictionary is then used as input to a password generator based on the famous XKCD 936 comic[2]. The idea is based on a similar tool Chris Angelico mentioned here several years ago[3], though as not a D&D player, I didn't have player chat available as user-specific input from which to construct a dictionary and chose email instead.
So much for background. After a long period of stasis, I decided to update polly to Python 3. While the 2-to-3 process was straightforward, I had problems after the update which looked like IMAP4 issues. I really didn't want to get knee deep in a pond full of IMAP alligators, so rather than bookmarking the IMAP4 RFC[4], I cast about for something higher level than imaplib, eventually settling on IMAPClient[5]. I thus have a collection of modules and packages: imapclient, imaplib, ssl, socket, and many other non-network bits. IMAPClient did what I wanted, for the most part abstracting away IMAP4 details. I still have to craft a couple IMAP4 parameter strings, but the rest of the interface is pretty Pythonic. However... Network applications being what they are, hiccups are going to happen. In the time since I swapped in the imapclient package, I've also had to catch exceptions raised by lower level modules/packages I wasn't using directly, discovering them only as they occurred. (Think of it as lazy exception discovery. I suppose if I was developing the application for others, I'd have been more proactive about uncovering the exceptions.) In addition to a couple imapclient exceptions, I also now need to catch socket.gaierror, ConnectionError and imaplib.IMAP4.error. Here's the crux of the problem. Where does responsibility generally fall for low level exception handling? I don't mean to pick on IMAPClient. It's just a recent example and got me thinking about the problem. Is it (generally) the responsibility of the application author or the package author? This isn't an issue just for network applications with a number of moving parts (socket, ssl, higher level packages, etc). It happens in almost all applications or packages, even if it's just to deal with exceptions raised by internal data structures. Skip [1] https://github.com/smontanaro/polly [2] https://xkcd.com/936/ [3] https://mail.python.org/pipermail/python-list/2014-August/827854.html [4] https://tools.ietf.org/html/rfc3501 [5] https://pypi.org/project/IMAPClient/ -- https://mail.python.org/mailman/listinfo/python-list
