collections模块

collections模块

一、导入方式

from collections import xxx

二、作用

复杂的数据类型

三、方法

3.1 有名元组

from collections import namedtuple
point = namedtuple('point',['x','y'])
p = point(1,2)
print(p.x)
print(p.y)
---------------------------------------------------
1
2

3.2 默认字典

from collections import defaultdict
# dic = {'a':1}
# print(dic['b'])
dic = defaultdict(lambda :'nan')  # dic = {}  # 如果找不到赋了一个默认值
dic['a'] = 1
print(dic['a'])
print(dic['c'])  #找不到关键字c给c赋了一个默认值nan
----------------------------------------------------------
1
nan

3.3 双端队列

# lis = [1,2,3]  # 线性表
# lis.append(4)   #在后面追加4
# print(lis)
from collections import deque  # 链表

de = deque([1,2,3])   
de.append(4)  #在最后面追加4
print(de)
de.appendleft(0)   #在最前面追加0
print(de)   # 默认删除左边的
de.popleft()
print(de)
-------------------------------------------------------------
deque([1, 2, 3, 4])

3.4 计数器

'''比较麻烦的方法'''
s= 'programming'
# dic = {}
# for i in s:
#     if i in dic:
#         dic[i]+=1
#     else:
#         dic[i] =1
# print(dic)
-------------------------------------------------------------
{'p': 1, 'r': 2, 'o': 1, 'g': 2, 'a': 1, 'm': 2, 'i': 1, 'n': 1}

# 新方法
from collections import Counter
s= 'programming'
c = Counter()  # 字典
for i in s:
    c[i] +=1   #在内部自己进行了一个判断
print(c)
-----------------------------------------------------
Counter({'r': 2, 'g': 2, 'm': 2, 'p': 1, 'o': 1, 'a': 1, 'i': 1, 'n': 1})