Not always though. I don't know if this is still the case, but "while true" used to be more idiomatic in Python than "while 1" even though the latter had better performance due to the state of the cpython implementation at the time.
It may be the case that at any given point, the idiomatic way is not the fastest. However, if idioms are widely adopted, the language implementers have good reason to optimize them. I'm not saying that's what happened in this case, but I think it's reasonable claim to make in general.
