$ p4 changes dest/...@lower,upper returns the changes submitted into dest.
$ p4 changes -i dest/...@lower,upper includes the changes that were integrated into dest.

changes = set(P4.run_integrated('dest/...@lower,upper'))
changes_with_integrated = set(P4.run_integrated('dest/...@lower,upper'))
integrated_changes = changes_with_integrated.difference(changes)