kill-ring-save rectangle and paste transposed?

Question

Suppose I have some code written like:

a_to_b = self.tversky(a, b)
b_to_c = self.tversky(b, c)
d_to_e = self.tversky(d, e)
e_to_f = self.tversky(e, f)
g_to_h = self.tversky(g, h)

I would like to select as a rectangle the variable names x_to_y and then paste it into array as so:

return [a_to_b, b_to_c, d_to_e, e_to_f, g_to_h]

I don't necessarily need the commas in one command, but basically selecting a few columns and then applying M-S ^ to each line. So I can get them all next to each other.

Answer 1

1. Select the rectangle (e.g. use C-x SPC).

2. Use this command (M-x foo) to copy the variables to the kill-ring, as the string "a_to_b, b_to_c, d_to_e, e_to_f, g_to_h":

(defun foo (beg end)
  (interactive "r")
  (let ((vars  (mapconcat #'identity
                          (extract-rectangle (region-beginning) (region-end))
                          ", ")))
    (kill-new vars)))

3. Move to where you want the result.

4. Use this command (M-x bar) to insert the result at point.

(defun bar ()
  (interactive)
  (insert "return [")
  (yank)
  (insert "]\n"))