How is it not general knowledge? How do you otherwise gauge if your program is taking a reasonable amount of time, and, if not, how do you figure out how to fix it?

But these performance numbers are meaningless without some sort of standard comparison case. So if you measure that e.g. some string operation takes 100ns, how do you compare against the numbers given here? Any difference could be due to PC, python version or your implementation. So you have to do proper benchmarking anyway.

You gauge with metrics and profiles, if necessary, and address as needed. You don’t scrutinize every line of code over whether it’s “reasonable” in advance instead of doing things that actually move the needle.