Python Learning Diary Fifth article--collections series

First, counter (counter)

The counter (counter) returns the number of occurrences of each character in a sequence as a dictionary, a value of key, and a number of values

#!/usr/bin/env python#-*-coding:utf-8-*-#导入collections模块import collectionscounter_test = collections. Counter ("ASFAFJHADGKHJKGFJHGFJHAGHDG") print (counter_test) #返回值C: \python27\python27.exe d:/cto3/day6/coun_1. Pycounter ({' G ': 5, ' H ': 5, ' a ': 4, ' F ': 4, ' J ': 4, ' d ': 2, ' K ': 2, ' s ': 1})

1, the Counter method (dictionary method slightly)

Counter is a subclass of Dict, all of which have all the methods of the dictionary, and some of their own methods

#取前3位的返回值ret1 = Counter_test.most_common (3) print (RET1) ######### #result: [(' G ', 5), (' H ', 5), (' A ', 4)] #循环取计数器中的值for k,v In Counter_test.items (): Print (k,v) ######### #result:(' a ', 4) (' d ', 2) (' G ', 5) (' F ', 4) (' H ', 5) (' K ', 2) (' J ', 4) (' s ', 1) #up The date method, subtract method, updates with the removal of obj = collections. Counter ([11,22,33,22,]) print (obj) obj.update ([11,22,44]) print (obj) obj.subtract ([11,22,44]) print (obj) ########## Result:counter ({22:2, 33:1, 11:1}) Counter ({22:3, 11:2, 33:1, 44:1}) Counter ({22:2, 33:1, 11:1, 44:0})

Second, ordered dictionary (ordereddict)

An ordered dictionary (ordereddict) is a subclass of a dictionary that records the order in which elements are added, based on a dictionary

#导入collections模块import Collectionsdic = collections. Ordereddict () dic[' k1 '] = ' v1 ' dic[' k2 '] = ' v2 ' dic[' K3 '] = ' v3 ' Print (DIC) ######### #result: ordereddict ([' K1 ', ' v1 '), (' K2 ', ' V2 '), (' K3 ', ' v3 ')])

1, the method of the ordered dictionary (the method of the dictionary slightly)

#python3中新加入的方法, move the dictionary in order dic.move_to_end (' K1 ') print (DIC) ######### #result: ordereddict ([' K2 ', ' V2 '), (' K3 ', ' V3 '), ( ' K1 ', ' v1 ')]) #按照顺序, LIFO popup element (with return value) Dic.popitem () print (DIC) ######### #result: ordereddict ([' K1 ', ' v1 '), (' K2 ', ' V2 ')] #指定弹出的元素 (with return value) Dic.pop (' K2 ') print (DIC) ######### #result: ordereddict ([' K1 ', ' v1 '), (' K3 ', ' v3 ')]) #更新, The Update method dic.update ({' K1 ': ' New1 ', ' K4 ': ' v4 '}) print (DIC) ######### #result: ordereddict ([' K1 ', ' New1 '), (' K2 ', ' V2 '), ( ' K3 ', ' V3 '), (' K4 ', ' v4 ')])

Third, default dictionary (defaultdict)

The difference between a default dictionary and a dictionary is that you can set the type of its elements

#导入collections模块import collectionsmy_dict = collections.defaultdict (list) my_dict[' K1 '].append (' v1 ') print (my_dict) ######### #result:d efaultdict (<class ' list ', {' K1 ': [' v1 ']})

Example:

#  Exercise: Element classification #  has the following value collection  [11,22,33,44,55,66,77,88,99,90...],#  saves all values greater than  66  to the first key in the dictionary, Save the value less than  66  to the value of the second key. #  namely:  {' K1 ':  greater than 66 ,  ' K2 ':  is less than 66}1, do not use the default pointing to determine whether the dictionary has {' K1 ': []}all_list =  [11,22,33,44,55,66,77,88,99,90,]dic = {}for i in all_list:     if i > 66:        if  "K1"  in  Dic.keys ():             dic[' K1 '].append (i)          else:             dic[' K1 '] = [i,]    else:         if  "K2"  in dic.keys ():             dic[' K2 '].append (i) &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;ELSE:&NBSP;&NBSP;&NBSP;&NBSP;&NBsp;       dic[' K2 '] = [i,]print (DIC) 2, default dictionary all_list = [ 11,22,33,44,55,66,77,88,99,90,]dic = collections.defaultdict (list) For i in all_list:     if i > 66:        dic[' K1 '. Append (i)     else:        dic[' K2 '].append (i) Print (DIC) ######### #result:d efaultdict (<class  ' list ' >, {' K2 ':  [11, 22, 33, 44,  55, 66],  ' K1 ':  [77, 88, 99, 90]})

Four, can be named Ganso (namedtuple)

The difference between namedtuple and tuples is that Namedtuple creates a class that contains a tuple and a specific method of its own

#导入collections模块import collections# creates a class that can be named tuples Mytupleclass = collections.namedtuple (' Mytupleclass ', [' X ', ' y ', ' z ') # Create object, obj object x=11,y=22,z=33obj = Mytupleclass (11,22,33) print (obj.x) print (OBJ.Y) print (obj.z) ######### #result : 112233

Five, queue

1. Bidirectional queue

#导入collections模块import  collectionsd = collections.deque (' Ghi ') Common methods: #右加入 >>>  D.append (' j ') #左加入 >>> d.appendleft (' F ') >>> ddeque ([' F ',  ' g ',  ' h ',  ' I ',  ' J ']) #右移除 (with a return value) >>> d.pop () ' J ' #左移除 (with a return value) >>> d.popleft () ' F ' >>>  ddeque ([' G ',  ' h ',  ' I ']) #队列可转换为列表 >>> list (d) [' G ',  ' h ',  ' I '] #右扩展 >> > d.extend (' JKL ') >>> ddeque ([' G ',  ' h ',  ' I ',  ' j ',  ' K ',  ' l ']) #左扩展 (reverse join queue) >>> d.extendleft (' abc ') >>> ddeque ([' C ',  ' B ',  ' a ',  ' G ',   ' h ',  ' I ',  ' j ',  ' K ',  ' l ']) #右轮换 >>> d.rotate (1) >>> ddeque ([ ' L ',  ' g ',  ' h ',  ' I ',  ' j ',  ' K ']) #左轮换 >>> d.rotate ( -1) >>>  Ddeque ([' G ',  ' h ',  ' I ',  ' j ',  ' K ',  ' l ']) #统计队列中元素出现的次数 >>> d.extend (' Ghijk ') ) >>> ddeque ([' G',  ' h ',  ' I ',  ' g ',  ' h ',  ' I ',  ' j ',  ' K ']) >>> d.count (' G ') clear >>> d.clear ()

2. One-way queue (FIFO)

Import queue# Create a one-way queue q = queue. Queue () #插入第一条数据q. Put (' 123 ') #插入第二条数据q. Put (' 456 ') #查看队列中有几条数据print (Q.qsize ()) #顺序取出第一条数据print (Q.get ()) ########## Result:2123

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Python Learning Diary Fifth article--collections series