collections模块内置数据结构扩展__lzy

collections模块内置数据结构扩展

1.namedtuple()

• factory function for creating tuple subclasses with named fields

• namedtuple让tuple属性可读

  import collections
  # 定义一个点
  Point = collections.namedtuple("Point", "x, y")
  p = Point(1, 2)
  p.x  # 1
  p.y  # 2
  p[0]  # 1
  p[1]  # 2
  

2.deque

• list_like container with fast appends and pops on either end

• deque可以方便地实现queue、stack

  # 创建一个双向队列
  de = collections.deque()
  
  # 左右两端添加
  de.append(1)
  de.appendleft(2)
  
  # 左右两端pop出
  de.pop()
  de.popleft()
  

3.Counter

• dict subclass for counting hashable objects

• 一个计数器工具提供快速和方便的计数

  c = collections.Counter("abcdab")  # Counter({"a": 2, "b": 2, "c": 1, "d": 1})
  c["a"]  # 2
  c.most_common()  # [('a', 2), ('b', 2), ('c', 1), ('d', 1)]
  
  

4.OrderedDict

• dict subclass that remembers the order entries were added

• 有序词典就像常规词典一样，但有一些与排序操作相关的额外功能。

  od = collections.OrderdDict()
  od['c'] = 'c'
  od['a'] = 'a'
  od['b'] = 'b'
  

5.defaultdict

• dict subclass that calls a factory function to supply missing values

  dd = collections.defaultdict(int)
  dd['a']  
  dd['b'] += 1
  dd  # defaultdict(int, {'a': 0, 'b': 1})
  

6.redis LRUCache实现原理

• 利用python内置的dict + collections.OrderdDict实现
• dict 用来当做k/v键值对的缓存
• OrderedDict 用来实现更新最近访问的key