Adding and traversing methods for key-value pairs in Python dictionaries _python

Add a key value pair

Define an empty dictionary first

>>> dic={}

To add a key that does not exist in the dictionary directly.

>>> dic[' name ']= ' Zhangsan '
>>> dic

{' name ': ' Zhangsan '}

If key or value are variables, you can use this method

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

{' Age ': ' Name ': ' Zhangsan '}

Here you can see the data in the dictionary is not in order, if interested, you can search the data structure of--hash table

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 ': ' Name ': ' Zhangsan ', ' sex ': ' Male '}

Traverse Dictionary

There are two ways of doing this.

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

>>> for key in dic:
...   print ' key is%s,value '%s '% (Key,dic[key])
...
The key is Id,value is 001 The key is Age,value is-is-
Name,value is Zhangsan The 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 '%s '% (key,value) ...
The key is Id,value is 001 The key is Age,value is-is-
Name,value is Zhangsan The key is Sex,value is
male

If you are unfamiliar with lists, tuples, and sequences, it is best to have a look at Baidu and understand them in depth. Can be understood in conjunction with arrays, list classes, and hash tables in your familiar C # or Java language

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