关于列表中元素筛选的有关问题

关于列表中元素筛选的问题
大家好，我有个问题想请教一下大家，我想对一个列表进行处理，除去列表中一些元素。具体如下：
m=[[1,2,3,4,5,6,7,8,9,10,11,12,13],[7,9,13,15,16,17,18,19,20,21,22,23],[17,19,20,21,22,23,24,25,26,27,28,19],[24,25,27,30,31,32,33,34,35,36,37,38,39,49,50],[3,4,5,6,7,8,33,45,46,47,56,57,58,59],[46,47,58,70,71,83,54,65,76,81,93,94],[100,101,102,103,104,105,106,107,120,121,123,125,146,147],[89,90,91,95,103,104,105,137,148,159,198,199,201]]
列表m的子列表个数还可以增加，我的目标是对列表m中的子列表进行处理，使后面的子列表不含之前子列表里面的元素，想问下大家有没有比较简单的方法，非常感谢！

------解决方案--------------------
子列表转成set处理...
------解决方案--------------------

Python code

m=[[1,2,3,4,5,6,7,8,9,10,11,12,13],
    [7,9,13,15,16,17,18,19,20,21,22,23],
    [17,19,20,21,22,23,24,25,26,27,28,19],
    [24,25,27,30,31,32,33,34,35,36,37,38,39,49,50],
    [3,4,5,6,7,8,33,45,46,47,56,57,58,59],
    [46,47,58,70,71,83,54,65,76,81,93,94],
    [100,101,102,103,104,105,106,107,120,121,123,125,146,147],
    [89,90,91,95,103,104,105,137,148,159,198,199,201]
    ]
processed = set()
for sublist in m:
    sublist = [item for item in sublist
        if item not in processed]
    map(processed.add, sublist)
    print sublist