If you're like me and addicted to using the old-school percent-symbol based string format, the newer bracket-based formatting is probably a bit mysterious. The python docs certainly don't help, they seem to be written for C programmers on meth (a help document entitled 'string format specification mini language' does not scream 'usability' to me, at any rate).
So, many props to Marcus Kazmierczak for his handy Python String Formatting Cookbook page. It's already saved me a ton of profanity. Here's to elevating the discourse of the internet!