Python笔记24-----生成器的使用（如嵌套列表的展开、树的遍历等）

def flatten(nested):
    if type(nested)==list:
        for sublist in nested:
            for i in flatten(sublist):
                yield i
    else:
        yield nested
print(list(flatten([[[1],2],3,4,[5,[6,7]],8])))

#结果为[1,2,3,4,5,6,7,8]

    def postorderTraversal(self, root):
        def iter(root):
            if root:
                for x in iter(root.left):
                    yield x
                for x in iter(root.right):
                    yield x
                yield root.val
        return list(iter(root))