简单掌握Python的Collections模块中counter结构的用法

from collections import Counter

>>> c = Counter('hello,world')
Counter({'l': 3, 'o': 2, 'e': 1, 'd': 1, 'h': 1, ',': 1, 'r': 1, 'w': 1})

 | __init__(self, iterable=None, **kwds)
 |  Create a new, empty Counter object. And if given, count elements
 |  from an input iterable. Or, initialize the count from another mapping
 |  of elements to their counts.
 |
 |  >>> c = Counter()       # a new, empty counter
 |  >>> c = Counter('gallahad')     # a new counter from an iterable
 |  >>> c = Counter({'a': 4, 'b': 2})   # a new counter from a mapping
 |  >>> c = Counter(a=4, b=2)     # a new counter from keyword args

>>> c = Counter(numbers) # c 存储了每个数字的频率
>>> c.most_common()  # 所有数字按照频率排序。如果 most_common 接受了 int 参数 n，将返回频率前n 的数据，否则会返回所有的数据
[('1', 8),
 ('2', 6),
 ('6', 6),
 ('5', 5),
 ('4', 5),
 ('7', 5),
 ('0', 3),
 ('9', 3),
 ('8', 2),
 ('3', 1)]

print('Counter类型的应用') 
c = Counter("dengjingdong") 
#c = Counter({'n': 3, 'g': 3, 'd': 2, 'i': 1, 'o': 1, 'e': 1, 'j': 1}) 
print("原始数据：",c) 
print("最多的两个元素：",c.most_common(2))#输出数量最多的元素 
print("d的个数：",c['d'])#输出d的个数 
print(c.values())#输出字典的value列表 
print(sum(c.values()))#输出总字符数 
print(sorted(c.elements()))#将字典中的数据，按字典序排序 
print('\n\n') 
""" 
#删除所有d元素 
del c['d'] 
b = Counter("dengxiaoxiao") 
#通过subtract函数删除元素，元素个数可以变成负数。 
c.subtract(b) 
""" 
 
""" 
可以添加数据 
b = Counter("qinghuabeida") 
c.update(b) 
"""