python中list可以嵌套吗

def nested_list(list_raw,result):

    for item in list_raw:

        if isinstance(item, list):

            nested_list(item,result)

        else:

            result.append(item)

    return  result  

def flatten_list(nested):

    if isinstance(nested, list):

        for sublist in nested:

            for item in flatten_list(sublist):

                yield item

    else:

        yield nested

def main():  

    list_raw = ["a",["b","c",["d"]]]

    result = []

    print "nested_list is:  ",nested_list(list_raw,result)

    print "flatten_list is: ",list(flatten_list(list_raw))

main()

nested_list is:   ['a', 'b', 'c', 'd']

flatten_list is:  ['a', 'b', 'c', 'd']

def dup_remove_set(list_raw):

    result = set()

    for sublist in list_raw:

        item = set(sublist)

        result = result.union(item)

    return list(result)

def main(): 

    list_dup = [[1,2,3],[1,2,4,5],[5,6,7]]

    print dup_remove_set(list_dup)

[1, 2, 3, 4, 5, 6, 7]

def dup_remove(list_raw,result):

    for item in list_raw:

        if isinstance(item, list):

            dup_remove(item,result)

        else:

            result.add(item)

    return  list(result)

def main():  

    list_raw = ["a",["b","c",["d","a","b"]]]

    result = set()

    print "dup_remove is:  ",dup_remove(list_raw,result)

dup_remove is:   ['a', 'c', 'b', 'd']