Python Basics: Dictionary

About 0x00

Dictionaries (dictionary) are unordered, cannot be accessed by offsets, and can only be read by keys. DIC is a mutable type, but the keys that make up the dictionary must be immutable data types, such as numbers, strings, tuples, and so on.

Syntax: dic = {' key ': value}

0X01 Basic Operations

Two ways to define

>>> ainfo = {'name':'xiaoming'Gender  ':'male'}>>> binfo = dict (name='  Xiaoming', gender='male')

Nesting and modifying

>>> Binfo = {'a': [+],'b': [4,5,6]}#nested lists in dictionaries>>>binfo{'a': [1, 2, 3],'b': [4, 5, 6] }
>>> binfo['a'][2] = 5#value can be modified in-place and is a mutable type>>>binfo{'a': [1, 2, 5],'b': [4, 5, 6]}

Two methods to add

>>> info = {'name':'xiaoming','Gender':'male'}>>> info[' Age'] = 10#single add key and value>>>info{'name':'xiaoming','Gender':'male',' Age': 10}>>> info = {'name':'xiaoming','Gender':'male'}info.update ({' Age': 11,' City':'Shanghai'})#if the key for update already exists, the original value is overwritten, and if key does not exist, it is created>>>info{'name':'xiaoming','Gender':'male',' Age': 11,' City':'Shanghai'}

Three ways to delete

Del

>>>info = {'name':'xiaoming','Gender':'male',' Age': 11,' City':'Shanghai'}>>>delinfo[' City']#just delete the city key>>>delInfo#Delete Info this dic

Clear

>>> a = {'info':'info','age' '=22}>>> a.clear ()

Pop

>>> A = {'name':'Sam',' Age': 22}>>> A.pop (' Age')#Pass in the key that needs to be deleted, return value, and delete from the dictionary22>>>a{'name':'Sam'}>>> A.pop ('Wealth','The key want to pop does not exist') #设置一个默认值 to prompt the Pop object when it does not exist 'The key want to pop does not exist'

Note: When the list uses the Pop method, the index is specified as subscript, such as A.pop (0), and the dictionary specifies the key name when using the Pop method.

Has_key method: Judge a key when it is included in the dictionary

>>>women.has_key ('dick') False

Return a key or value individually as a list

>>> info = {'name':'Jerry' Age '=23}>>> info.keys () ['name','  Age ' ]>>> info.values () ['Jerry', 23]

Items: Creating a container for a dictionary

>>> info = {'name':'Jerry' Age '=23}>>> info.items () [('name':'  Jerry'), (' Age': +)]

Get: Return value by Key name

>>> info = {'name':'Jerry',' Age'=23}>>> Info.get ('name')'Jerry'>>> Info.get ('Gender','Do not exist')#when the key name of get does not exist, return the following sentence'Do not exist'

Python Basics: Dictionary