Jason Whitehorn has written a library for Python to control/read the GPIO pins based on events. It means you can write code like:

watch :pin => 23 do
  puts "Pin changed from #{last_value} to #{value}"
end

#Or

after :pin => 23, :goes => :high do
  puts "Button pressed"
end

… which is very intuitive and is an excellent way of doing it.

Read more and download the library here