Simple mastery of the use of counter structures in Python's collections modules _python

Counter is a special kind of dictionary, which is mainly convenient for counting, the key is to count the number of Item,value saved.

From collections import Counter

>>> c = Counter (' Hello,world ')
Counter ({' L ': 3, ' O ': 2, ' E ': 1, ' d ': 1, ' H ': 1, ', ': 1, ' R ': 1, ' W ': 1}

Initialization can pass in three types of parameters: dictionaries, other iterable data types, and named parameter pairs.

 | __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 a 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

The default request, access to the nonexistent item, returns 0. Counter can be used to count the number of occurrences of some data, such as a very long number string numbers = frequency of each number in "67642192097348921647512014651027586741512651":

>>> C = Counter (numbers) # C stores the frequency of each number
>>> C.most_common ()  # All numbers are sorted by frequency. If the Most_common accepts the int parameter n, will return the data of the first n of the frequency, otherwise it will return all the data
[(' 1 ', 8),
 (' 2 ', 6), (' 6 ',
 6)
 , (' 5 ', 5
 ), (' 4 ', + 5),
 (' 7 ', 5),
 (' 0 ', 3),
 (' 9 ', 3), (
 ' 8 ', 2),
 (' 3 ', 1)]

In addition, you can also do two Counter objects +,-,min, Max and other operations.

Comprehensive Example:

Print (' Counter type application ') 
c = Counter ("Dengjingdong") 
#c = Counter ({' n ': 3, ' G ': 3, ' d ': 2, ' I ': 1, ' O ': 1, ' E ': 1, ' J ': 1} ' Print (" 
raw Data:", c) 
print ("Up to two elements:", C.most_common (2)) #输出数量最多的元素 
print (Number of "D:", 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, Sort print in dictionary order 
(' \ n ') "" " 
#删除所有d元素 
del c[' d '] 
B = Counter (" Dengxiaoxiao ") 
# By subtract function, the number of elements can become negative. 
C.subtract (b) "" "" " 
can add data 
B = Counter (" Qinghuabeida ") 
c.update (b)