Hi, reversed() results are fine until iterated over, after which the results are no longer available. This was discovered after using something like this:
rev = reversed( sorted( list ) ) sr = sum( 1 for _ in rev ) # rev is now destroyed So reversed() results can only be iterated once unlike sorted(), etc... Script to illustrate the issue: /tmp/rev: orig = [ 'x', 'a', 'y', 'b', 'z', 'c' ] co = sum( 1 for _ in orig ) print( 'orig', orig, co ) # reversing rev = reversed(orig) print( 'before iteration:', [ x for x in rev ] ) # list comprehension was an iteration over 'rev' print( 'after iteration:', [ x for x in rev ] ) # how this was discovered... orig = [ 'x', 'a', 'y', 'b', 'z', 'c' ] rev = reversed(orig) cr = sum( 1 for _ in rev ) print( 'after sum():', [ x for x in rev ] ) which produces: $ python /tmp/rev orig ['x', 'a', 'y', 'b', 'z', 'c'] 6 before iteration: ['c', 'z', 'b', 'y', 'a', 'x'] after iteration: [] after sum(): [] Regards, Pierre -- https://mail.python.org/mailman/listinfo/python-list
