J and Python Tips

J

$: self reference for recursion etc.

Have to experiment with it

Python

Use seq[:1] and seq[-1:] first and last instead of seq[0] and seq[-1] to avoid index out of range exception for empty sequences

Generally, for all index n use seq[n:n+1] instead of seq[n] to avoid exceptions without having to add extra logic checks

>>> [][3:4]

[]