It's no bad thing to import modules if they get the job done! There's a time and a place for code golf. That said - with the distance of several years' hindsight - I should probably have added a short comment.

Not sure if linking comments works here but there is a reply to MrSoto from a few years back where I expand the code with line by line explanation. Can expand on that if it's unclear, although it's been a while :-)

well now that's just verging on unreadable :-)

Ah :-D that'd do the trick. I'm a blind ... mouse, I guess. Thanks!

Perhaps I misunderstand, but there seems to be a bug in the second annotated example (Python):

            ↗    row 0
    P ↓   ↖ ↑    row 1
        ←   ↓    row 2
      ↖ ↙   ↙    row 3
    ↓ ↓ ↓        row 4
col 0 1 2 3 4

The piper is at (row 1, col 0).
The rat at (row 3, col 2) is heading ↙ to (row 4, col 1),
so it was (2 rows + 2 cols) away, and will be (3 rows + 1 col) away.
Using Euclidean distance, this is a distance increase of sqrt(8) to sqrt(10) units,
i.e. the rat is heading away, but the example labels the rat as non-deaf.

Deaf rats have a hard enough life in Hamelin without being labelled as non-deaf! Any suggestions?

Thanks

lol, disregard. obviously that final line should be min(..)