[python] python vs Cplusplus

Some of the learning processes summarize the small contrasts between the two languages to help understand Oo Programming.

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Dictionary

• Series--dictionary

Python:

def get_counts (sequence):     = {}    for in  sequence:        if in counts:            + = 1        else:            = 1    #  This is a mishap, not better than C + +, here must be written     return counts

C + +: That doesn't seem to be the Problem.

#include <iostream>#include<map>using namespacestd;intmain () {cout<<"Hello world!"<<endl; Map<string,int>m;//m["a"] = 1;//m["a"] + = 1;cout<< m.size () <<endl; cout<< m["a"] <<endl; //automatically added "a" cout<< m.size () <<endl; return 0;}

• Dictionary sort

C + + sort Reference:

[c + +] Associative Containers

Python sort:

Counts = get_counts (time_zones)#  counts.sort () error, default sorted by first property print# Debug

What if it's a custom sort?

The Python dictionary (dict) is characterized by an unordered character that extracts the corresponding value (value) according to the KEY.

If we need a dictionary sorted by value , it can be done in the following way:

(1) the following values are sorted in order of value from large to Small.

DIC = {'a': 31,'BC'75A'C': 3,'ASD': 4,'AA': 74,'D': 0} #dic. iteritems () gets a list of [(keys, values)]. #然后用sorted方法, by the key parameter, specifies that the sort is sorted by value, or 2nd element d[1]. Reverse = True indicates that it needs to be flipped, the default is small to large, flip the words, that is, from large to Small. dict= Sorted (dic.iteritems (), key=Lambdad:d[1], reverse =True)PrintDict

(2) sort the dictionary key (key):

DIC = {'a'BC'c' ASD ' ' AA ' ' D ' : 0}dict= sorted (dic.iteritems (), key=Lambda# Sort print by the value of 2nd element d[1]  Dict

[python] python vs Cplusplus