This is less wat. when you write it like eager: for item in loop(): item() lazy: items = [] for item in loop(): items.append(item)

This is less wat. when you write it like eager: for item in loop(): item() lazy: items = [] for item in loop(): items.append(item) for item in items: item() Each next() into loop increments a shared counter so when you print it out as you go it 1, 2, 3 but when you print it out once you've called it a bunch is 9, 9, 9.