Order of evaluation; du() will be instantiated, sort() will be instantiated, and then du().__or__() is evaluated, which means you won't have du's stdout to atta

Order of evaluation; du() will be instantiated, sort() will be instantiated, and then du().__or__() is evaluated, which means you won't have du's stdout to attach to stdin on sort when it's instantiated. Figuring out a way around this (mocking up an fd to pass to sort at instantiation time that blocks until stdout on du is available) is left as an exercise to the reader. I've already said too much. ;)