(use-modules (gnu packages)
             (guix)
             (guix graph)
             (guix scripts graph))

(define all
  (fold-packages cons '() #:select? (const #t)))

(with-store store
  (let ((back-edges (run-with-store store
                      (node-back-edges %bag-node-type all))))
    (define (unused-python2? package)
      (and (string-prefix? "python2-" (package-name package))
           (zero? (node-reachable-count (list package)
                                        back-edges))))
    (for-each (lambda (package)
                (when (unused-python2? package)
                  (format #t "~a~%" (package-name package))))
              all)))