On 29 August 2013 10:07, Chris Angelico <ros...@gmail.com> wrote: > Hmm. l don't know of any good articles off-hand. But what I'm talking > about is simply developing the skill of reading exceptions, plus a few > simple things like knowing where it's appropriate to catch-and-log; > sometimes, what that means is actually writing some code to (for > example) email you whenever there's an exception, but more likely it > means writing no code at all, and just looking at STDERR of your live > usage. Works really well for >95% of Python scripts. > > The most important thing to consider is: What happens if my code > doesn't run all the way through? Is it safe for this to run part way, > then bomb with an exception? For many scripts, it's pretty easy: fix > the problem and rerun the script, and it'll completely rewrite its > output file. For others, this is a good reason for putting all your > "real data" into a transactional database - you begin a transaction at > the top, don't commit till the end, and if an exception kills your > script, your transaction will be rolled back. I have a system for > patching our database based on a script (written in Pike, not Python, > but the same applies); if I have any sort of critical failure in the > patch script, it'll bomb out as soon as I test it - but since I use > PostgreSQL, all that DDL (eg "ALTER TABLE") is covered by > transactional integrity (which it isn't with MySQL - another reason to > be wary of MySQL), so my patch will be backed out, and I can fix it > and start over. I don't need to have a Look Before You Leap approach > to database changes - I can simply do stuff, and if it crashes, all's > well. (That same script also has a system for catching errors at a > mid-level point that means that the process doesn't terminate when > there's an error; it supports full code reload, so once I fix the > patch, I send the process a SIGHUP and it fetches from disk again.) > *That* is error handling the safe way. >
Oh, I get it! Thanks. -- http://mail.python.org/mailman/listinfo/python-list
