> You don’t seem open to consider what I am saying, rather in a rush to demand some kind of “proof” with no willingness to think through it it doesn't work thi

> You don’t seem open to consider what I am saying, rather in a rush to demand some kind of “proof” with no willingness to think through it it doesn't work this way, if you state something to be true, the burden of proof lies on your shoulders and I am open to consider the proof, and not just words alone. It's funny that this subthread was started with a statement that my example of complexity estimation difficulties was deeply contrived, yet the examples for a proof of generators' inefficiences materialize all intermediate values into lists. Why would I want to materialize a list to yield something from it later, if I can just pass the range() stream to the caller instead? Your second example is an exemplary code smell, as there's no need for a helper() closure. And there's no need to hold resources for check_expensive_in(), as most of DBs have lazy query cursor implementations in one way or the other. Afterall, it's not about doing everything in one expensive DB call and laziness doesn't negate buffered data, it just says that there's an explicit boundary on internal buffers within a single iteration, and every single iteration may perform a separate but less expensive DB call.