The addition and traversal methods of python dictionary key value pairs

Add a key-value pair

First, define an empty dictionary

> > > dic={}

Add by assigning key directly to a dictionary that does not exist

>>> dic['name']='zhangsan'
>>> dic

{'name': 'zhangsan'}

You can do this if key or value are both variables

>>> key='age'
>>> value=30
>>> dic[key]=value
>>> dic

{'age': 30, 'name': 'zhangsan'}

Here you can see that the data in the dictionary is not sorted in order. If you are interested, you can search for the hash table in the data structure

You can also use the setdefault method of the dictionary

>>> dic.setdefault('sex','male')
'male'
>>> key='id'
>>> value='001'
>>> dic.setdefault(key,value)
'001'
>>> dic
{'id': '001', 'age': 30, 'name': 'zhangsan', 'sex': 'male'}

Through the dictionary

There are two ways to do it

Method 1: get key first, then value via dic[key]

>>> for key in dic:
...   print 'key is %s,value is %s'%(key,dic[key])
...
key is id,value is 001
key is age,value is 30
key is name,value is zhangsan
key is sex,value is male

Method 2: sequence unpack the list of tuples returned by the dictionary items() method

>>> for key,value in dic.items():
...   print 'key is %s,value is %s'%(key,value)
...
key is id,value is 001
key is age,value is 30
key is name,value is zhangsan
key is sex,value is male

If you are not familiar with lists, tuples, and sequence unpacking, it is best to go to baidu 1 and understand them in depth. You can combine arrays, List classes, and hash tables in your familiar C# or JAVA languages