1. collections.deque() append() appendleft() pop() popleft() --O(1) 2. collections.OrderedDict() KEY's order is the insertion order! 3. defaultdict() from collections import defaultdict stats = defaultdict(int) stats['my_counter'] += 1 normal dict: stats = {} key = 'my_counter' if key not in stats: stats[key] = 0 stats[key] += 1 --->[] can't take the case where key is not in! so we have to pay attention to that! 4. heapq / PriorityQueue() qut() get() --> O(lgn) from queue import PriorityQueue q = PriorityQueue() q.put(4) q.put(2) q.put(5) q.put(1) q.put(3) while not q.empty(): next_item = q.get() print(next_item) 5. bisect 二分法 -> O(logN) bisect(list, num, beg,end)-->upper bound bisect_left(list, num, beg,end)-->lower bound