collections

#!/usr/bin/env python3
# _*_ coding:utf-8 _*_
# ========================================================
# Module         :  collections
# Author         :  luting
# Create Date    :  2018/6/4
# Amended by     :  luting
# Amend History  :  2018/6/4
# ========================================================

# collections => python内建集合模块
# namedtuple  => 创建自定义tuple对象，并规定tuple元素个数，可以使用属性来引用tuple元素
from collections import namedtuple

point = namedtuple('POINT', ['X', 'Y'])
p = point(1, 2)
print(p.X, p.Y)


# deque => 为了高效实现插入和删除操作的双向列表， 适合用于队列和栈
from collections import deque

# 支持append/pop/appendleft/popleft
q = deque(['a', 'b', 'c'])
q.append('x')
q.appendleft('y')
print(q)


# defaultdict => key不存在时，返回一个默认值
from collections import defaultdict

dd = defaultdict(lambda: 'N/A')
dd['key1'] = 'abc'
print(dd['key2'])


# orderdict => 保持key的顺序
from collections import OrderedDict

od = OrderedDict([('a', 1), ('b', 2), ('c', 3)])
print(od, dict([('a', 1), ('b', 2), ('c', 3)]))


# Counter => 是一个简单的计数器
from collections import Counter
c = Counter()
for ch in 'programming':
    c[ch] += 1
print(c)