How do I renumber block tags in order automatically in AutoCAD?

What cadssistant does

1. Selects the DOOR-TAG inserts that carry attributes ((66 . 1) in the filter) and reads each one's insertion point and NUMBER attribute.
2. Sorts by Y descending (rows), then X ascending within a row, with a row tolerance (the snippet uses 50 units; say the tag spacing if rows are tight).
3. Writes D01, D02 … into the NUMBER attribute of each in one AutoLISP pass; a REGEN or entupd shows the new values if the screen doesn't refresh on its own.
4. Replies with handle, old and new in a table, so a wrong row order is easy to spot and revert.

The same task in AutoLISP

(progn
  (vl-load-com)
  (setq ss (ssget "_X" '((0 . "INSERT") (2 . "DOOR-TAG") (66 . 1))) i 0 lst nil n 1)
  (if ss
    (repeat (sslength ss)
      (setq e (ssname ss i) i (1+ i))
      (setq lst (cons (cons e (cdr (assoc 10 (entget e)))) lst))))
  (setq lst (vl-sort lst '(lambda (a b)
    (if (equal (caddr a) (caddr b) 50.0) (< (cadr a) (cadr b)) (> (caddr a) (caddr b))))))
  (foreach item lst
    (setq att (entnext (car item)))
    (while (and att (= (cdr (assoc 0 (entget att))) "ATTRIB"))
      (if (= (cdr (assoc 2 (entget att))) "NUMBER")
        (entmod (subst (cons 1 (strcat "D" (if (< n 10) "0" "") (itoa n)))
                       (assoc 1 (entget att)) (entget att))))
      (setq att (entnext att)))
    (entupd (car item))
    (setq n (1+ n)))
  (1- n))

Tags whose Y is within 50 units count as one row; change 50.0 to suit the plan. Returns how many were renumbered.

Good to know

• "Reading order" is rows from the top; say "clockwise from the entrance" or "by room number" and the sort changes accordingly.

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