leetcode284

 1 class PeekingIterator:
 2     def __init__(self, iterator):
 3         self.iterator = iterator
 4         self.head = iterator.next()
 5 
 6     def peek(self):
 7         return self.head
 8 
 9     def next(self):
10         res = self.head
11         self.head = self.iterator.next() if self.iterator.hasNext() else None
12         return res
13 
14     def hasNext(self):
15         return self.head != None