# """
# This is the interface that allows for creating nested lists.
# You should not implement it, or speculate about its implementation
# """
#class NestedInteger(object):
#    def isInteger(self):
#        """
#        @return True if this NestedInteger holds a single integer, rather than a nested list.
#        :rtype bool
#        """
#
#    def getInteger(self):
#        """
#        @return the single integer that this NestedInteger holds, if it holds a single integer
#        Return None if this NestedInteger holds a nested list
#        :rtype int
#        """
#
#    def getList(self):
#        """
#        @return the nested list that this NestedInteger holds, if it holds a nested list
#        Return None if this NestedInteger holds a single integer
#        :rtype List[NestedInteger]
#        """

class NestedIterator(object):

    def __init__(self, nestedList):
        """
        Initialize your data structure here.
        :type nestedList: List[NestedInteger]
        """
        self.data = nestedList
        self.last = []
        def flat(arr):
            for a in arr:
                if not isinstance(a,list):
                    yield a
                else:
                    # yield from flat(a) py2 not support yield from
                    for x in flat(a):
                        yield x
        self.gen = flat(self.data)
        

    def next(self):
        """
        :rtype: int
        """
        if self.hasNext():
            return self.last.pop()
        else:
            return None
        

    def hasNext(self):
        """
        :rtype: bool
        """
        if self.last:
            return True
        try:
            v = next(self.gen)
            self.last.append(v)
            return True
        except StopIteration:
            return False
        



nestedList = [[1,1],2,[1,1]]        
i, v = NestedIterator(nestedList), []
while i.hasNext():
    v.append(i.next())
print(v)

# Your NestedIterator object will be instantiated and called as such:
# i, v = NestedIterator(nestedList), []
# while i.hasNext(): v.append(i.next())