Sorry Doug, I don't find any of the suggestions to be an improvement and I concur with David Murray that the docstring for qsize() isn't the place for a tutorial on race conditions and LBYL vs EAPF which are general threading topics rather than a queue specific topics.

Also, I'm reluctant to change Guido's original wording which has served well for a decade.  While I'm sure you can invent ways to misread the word "approximate", it does communicate that this method cannot relied upon to return the exact size.  If we were seeing recurring source of confusion, there might be a basis for a change, but that is not the case.

Sorry, but I'm going to close this one.  Every person might find a different way to wordsmith this one, but I think we should favor Guido's choice.