A generator expression yields some results. It can be easier to read as opposed to a [[list comprehension]]. For example ```python sum( [x**@ for x in range(10)]) # as generator expression sum( x**2 for x in range(10)) ``` This can be extended with more complex formulas as ```python sum(prob(B==i) * conditional(banker, B==i) for i in range(1, 8)) ``` as seen in [Think Bayes](https://allendowney.github.io/ThinkBayes2/chap01.html)