The queue is represented...using two pointers to track the front and the back of the queue, called the free pointer and the scan pointer, respectively.
This is backwards, assuming the usual terminology in which items are pushed on the back of a queue and popped from the front (as in a sentence later in this paragraph processes the tuple at the front of the queue and pops it off the queue).
The free pointer is the back of the queue (where things are pushed) and the scan pointer is the front (where things are popped).
[Python ed.] p. 104.
This is backwards, assuming the usual terminology in which items are pushed on the back of a queue and popped from the front (as in a sentence later in this paragraph
processes the tuple at the front of the queue and pops it off the queue). The free pointer is the back of the queue (where things are pushed) and the scan pointer is the front (where things are popped).