* The garbage collector tries to avoid tracking simple containers which
can't be part of a cycle. As of now, this is true for tuples and dicts
containing atomic types (such as ints, strings, etc.). Transitively, a dict
- containing tuples of atomic types won't be tracked either. This helps brings
- down the cost of full garbage collections, since it decreases the number of
- objects to be considered and traversed by the collector.
+ containing tuples of atomic types won't be tracked either. This helps bring
+ down the individual cost of each garbage collection, since it decreases the
+ number of objects to be considered and traversed by the collector.
+
+ To help diagnosing this optimization, a new function in the :mod:`gc`
+ module, :func:`is_tracked`, returns True if a given instance is tracked
+ by the garbage collector, False otherwise.
(Contributed by Antoine Pitrou; :issue:`4688`.)