Reference counting: how Python knows when to throw an object away

Tap a name to move its label to the next box, or to remove it. Watch the counts. A box whose count reaches 0 is freed immediately.

Box 1 and Box 2 hold on to each other

Each name adds 1 to the box it points at. Try pointing every name at Box 1: Boxes 2 and 3 are freed as their last label leaves.