Recently, I stumbled over a small issue in Python's cgi module that is agood illustration of how unintended consequences in Python can wind upshooting you in the foot.

The cgi module 's main purpose is to create a dictionary-likeobject that contains all of the parameters passed to your CGI programin the GET or POST HTTP command. DWiki uses it roughly like this:

form = cgi.FieldStorage()for k in form.keys():  ... stuff ...

Then one

Once upon a time I wrote a program to scan incoming mail messages duringthe SMTP conversation for signs of spam. Because this was running aspart of our mailer, reliability was very important; unhandled errorscould cause us to lose mail.

As part of reliability, I decided I wanted to catch any unhandledexception (which would normally abort the program with a backtrace),log the backtrace, save a copy of the message that caused the bug, andso on. So I wrote code that went like this:

I cannot resist pointing to Jakob Nielsen's latest column, Weblog Usability: The Top Ten Design Mistakes .If you're interested in usability issues, and anyone interested inmaking effective web sites had better be, his columns are usuallyworthwhile. (One of my embarrassments is that I haven't been readinghim much lately; I used to care about this quite a lot.)

I think that Nielsen's weblog usability issues, like a fair amount ofhis writing, are aimed at what I would

If you haven't tested it, it doesn't work.

I got this from the Extreme Programming movement, but it's just asapplicable to systems and procedures as it is to developing software.(Remember verifying backups ? That's an instanceof this aphorism.)

This has an important corollary:

If you aren't checking it, it's broken.

For example, when you have a spiffy hardware RAID system you shouldmake very sure that you do indeed get notified when a disk