It’s been a technical week. Exclusion constraints are generalized SQL UNIQUE One of the cool new features of PostgreSQL 9.0 is exclusion constraints. Exclusion constraints make it possible to create a scheduling grid for a classroom or hotel that prevents double bookings of a room. Your Software Can Learn A Lot From ATMs ATMs are simple. They work. They work well. When they don’t work, they tell you that something is up, but they don’t do anything sneaky or have side effects or do two things at once. Do you want to take out money? Do you want a receipt? Do you want to deposit money? There aren’t multiple options with strange combinations. You do one things and then move on to the next. Your software should be like this. Gurus and Bastards What’ll it be? Helpful optimistic guru or grumpy bastard? Learn Python the Hard Way A fun new way to learn how to program: type the program, run the program, do the extra credit. txn.commit() are you sure? Think about whether you’re really using those transactions the right way. Think about it.