That's not what they mean. The usage they are discussing is more like this, I believe. In a functional context, instead of doing: print expensive_computati

That's not what they mean. The usage they are discussing is more like this, I believe. In a functional context, instead of doing: print expensive_computation(), expensive_computation() You can do: (lambda x: print x, x)(expensive_computation()) Which would be equivalent to, with an imaginary let syntax: (let x be expensive_computation(): print x, x)