Don't forget the "ON TRUE" part since it's still a JOIN, and the joining condition just moves inside the LATERAL statement. It's like running a for loop on the table preceding LEFT JOIN, where in each iteration one row from the lhs joins with rhs rows selected by the LATERAL (...) statements with no other constraints; hence the "ON TRUE" part.

Be very careful working with 2D list in Python: when indexing/referencing, list comprehensions like [[... for i in ...] for j in ...] work better than ':' such as in [a:b][c:d]. Also, indexing an empty list and assigning values to construct bigger list object is NOT VALID; have to use some of the list's default methods to modify it.

Sorry, it's not meant to be a Kumite. Please ignore the post.

NOTE: the calc_unit_length function used here is NOT error-free; the longer version in the other two sol's should be right.