A simple understanding of the counter structure usage in the Collections module of Python

The counter data structure is used to provide technical functions. it is similar to the built-in dictionary structure in Python. here we use a few small examples to briefly master the usage of the counter structure in the Python Collections module: counter is a special dictionary, which is mainly used for counting. The key is the item to be counted, and the value is the number.

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

Three types of parameters can be input during initialization: Dictionary, 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 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

By default, 0 is returned for items that do not exist during access. Counter can be used to count the number of occurrences of certain data, such as the frequency of each number in a long numeric string numbers = "67642192097348921647512014651027586741512651:

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

In addition, you can perform operations such as +,-, min, and max on two Counter objects.

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 ("two elements at most:", c. most_common (2) # print ("number of d:", c ['D']) of the most output elements # print (c. values () # print (sum (c. values () # print (sorted (c. elements () # sort the data in the dictionary in the lexicographically ordered print ('\ n \ n ') "# Delete all d elements del c ['D'] B = Counter (" dengxiaoxiao ") # Use The subtract function to delete elements The number of elements can be negative. C. subtract (B) "You can add data B = Counter (" qinghuabeida ") c. update (B )"""