for x in [ 1,2,3,4,5,6,7,8,9 ]:

    for y in [ 0,1,2,3,4,5,6,7,8,9 ]:

        if x < y:

            print x*10 + y

应该是格式问题，严格按照空4格的要求。以下是执行后的

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>>> for x in [ 1,2,3,4,5,6,7,8,9 ]:

                  for y in [ 0,1,2,3,4,5,6,7,8,9 ]:

                         if x<y:

                                print 10*x+y

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