One of the consequences of yesterday's SAN backend failure is that I found a bug in our spareshandling code. It was the kind of bug where the program aborts, and whenthat happens we started getting email with Python exception backtracesthat ended in what struck me as a very odd exception:

KeyError: False

Normally KeyErrors make a kind of sense, in that you see whatyou're looking up and the question is either why you wound up usingthat key or why that key isn't present when

One of my bad habits as a Python programmer is that I am both lazy andimpatient. I will go out of my way to do something overly clever justbecause it saves me some boring boiler-plate code, and because Python issuch a compact language already my threshold for this irritation is verylow.

One of the things that this leads me to is writing conditionalvariable initializations like this:

var = Noneif condition:    var = something()

I've recently come to the conclusion that this is a