Collections中的各种方法

一、各种方法介绍

Counter　　　　统计个数   elements  most_common  subtract

defaultdict 　　字典默认值

ChainMap  　　合并多个映射对象（字典）

OrderdDict  　  有顺序的字典

deque　　　　  双向队列，可限制长度 append,appendleft,ratote

namedtuple      命名元祖

二、代码部分

from collections import Counter, defaultdict, ChainMap, OrderedDict, deque, namedtuple

"1.Counter"
# 三个方法，在前面的博客词频统计有学习过。
s = 'de8g love python so much'
counter = Counter(s)
# print(counter, type(counter))
# print(list(counter.elements()))

print(counter.most_common(5))  # 排序
counter.subtract('o')          # 对某一个统计减少一次
print(counter.most_common(5))  # 排序

"2. 默认字典"
# 默认字典defaultdict 在lambda中学习过
defaultdict(lambda: 0)
defaultdict(lambda: 'abc')
c = defaultdict(lambda: (3,6))
c['a']
print(c)

# 默认字典在传统的统计里面使用
s = 'de8ug loves you so de8ug loves you so much you so much  much '
# count_spilt = {}
dc_words = defaultdict(int)  # 或者 lambda: 0
dc_words[10]
for i in s.split(' '):
    # if i in count_spilt:
    #     count_spilt[i] += 1
    # else:
    #     count_spilt[i] = 1
    dc_words[i] += 1
print(dc_words)

# 默认字典的赋值为空列表
line = [(1,2),(1,3),(3,6),(4,7),(3,9),(4,9),(5,10)]
# 把相同x的y 追加到列表中
# line_new = {1:[2,3],3:{6,9}}
line_new = {}
for x,y in line:
    if x not in line_new:
        line_new[x] = [y]
    else:
        line_new[x].append(y)
print(line_new)

# -----------------------
line_dic = defaultdict(list)  # 新做法
for x, y in line:
    line_dic[x].append(y)
print(line_dic)

"3. ChainMap "
# 把两个字典组合起来
d1 = {'debug':1,"louhui":2,"diaosi":3}
d2 = {1: [2, 3], 3: [6, 9], 4: [7, 9], 5: [10]}
chain = ChainMap(d1,d2)
d3 = {'louhui':'shuai', 'caoyu':4, 1:""}
chain.update(d3)
print(chain)

"4. OrderDict"
# 在python3 字典就是有序的，但是我们不能依赖他，可能会变化
# 传统做法
dict2 = {'': 2,'a': 3,'de8ug': 2,'e': 8,'k': 9,'loves': 2,'much': 3,'so': 3,'you': 3}
keys = dict2.keys()
sorted(keys)
for k in keys:
    print(k, dict2['e'])

# 使用OrderDict
dd = {'banana': 3, 'apple':4, 'pear': 1, 'orange': 2}
order_dic = Orderdd = {'banana': 3, 'apple':4, 'pear': 1, 'orange': 2}
#按key排序
kd = OrderedDict(sorted(dd.items(), key=lambda t: t[0]))
#按照value排序
vd = OrderedDict(sorted(dd.items(),key=lambda t:t[1]))

"5. deque"
# deque - double-end que.双向队列，支持线程安全
de = deque()
de.append(1)
de.append(2)
de.appendleft(3)
print(de)

de1 = deque([1,2,3,4,5,6,7], 7)
print(de1)
de1.rotate(3)  # 旋转
print(de1)

# 另外一个作用，tail类型。输出文件的最后几行
def tail_file(filename, n):
    with open(filename, 'r') as f:
        return deque(f, n)

print(tail_file('/Users/lh/my_learn_python/01-python/123.txt', 2))

"6. nametuple"
# 就是给元祖每个变量定义一个名字
# 三种命名格式
Point = namedtuple('Point', 'm,n')
Point = namedtuple('Point', 'm n')
Point = namedtuple('Point', ['x', 'y'])

# Ponit=namedtuple('Point-LH','x,y')
p = Point(1,2)
print(p)
print(p.x)