Python: The basic operation of a dictionary

The dictionary is the only type of mapping in Python. Dictionaries are mutable, unordered, variable-sized key-value mappings, sometimes called hash lists or associative arrays.

Examples are below:

DiC = {"Apple": 2, "orange":1}    #定义一个字典
>>> dic.copy ()     #复制字典
{' Orange ': 1, ' Apple ': 2}
>>> dic["banana"] = 5    #增加一项
>>> dic.items ()      #获得字典中成员的列表
[(' Orange ', 1), (' Apple ', 2), (' Banana ', 5)]
>>> dic.pop ("Apple", 3)      #删除 "Apple", if not Apple, returns 3
3
>>> dic
{' Orange ': 1, ' Banana ': 5}
>>> Dic.keys ()     #获得键的列表
[' Orange ', ' banana ']
>>> dic.values ()     # Get a worthwhile list
[1, 5]
>>> dic.update ({"Banana": 3})     #更新 "Banana" value
>>> dic
{ ' Orange ': 1, ' Banana ': 3}
>>> dic.update ({"Apple": 2})       #更新 "Apple" value, if not, Add
>>> dic
{' Orange ': 1, ' Apple ': 2, ' Banana ': 3}
>>> dic["Orange"]       #通过键获取值
1
>>> dic.clear ()      #清空字典

>>> DIC
{}

Look at one more of the following:

#创建一个初始字典, it contains a string and an integer. Their keys are all strings.

>>> book = {"title": "Python Web Development", "Year": 2008}

#显示这个对象.
>>> Book
{' Year ': +, ' title ': ' Python Web Development '}

#检查字典是否含有某个键, for Real.
>>> ' year ' in book
True

#检查字典是否含有某个键, for the false
>>> "Pub" in the book
False

#使用get方法获取给定键的值 (the default value is obtained here)
>>> Book.get ("Pub", "N/A")
' N/A '

#加入一个新的键-value pairs
>>> book["Pub"] = "Addison Wesley"

#再次使用get方法, but the success of this one gets the value
>>> Book.get ("Pub", "N/A")
' Addison Wesley '

#迭代整个字典并显示每一对键-Value
>>> for key in book:
Print key, ":", Book[key]

year:2008
Pub:addison Wesley
Title:python Web Development

Common methods in dictionaries:

Dic.clear (): Empty dictionary

Dic.copy (): Copy dictionary

Dic.get (k): Gets the value of the key K

Dic.has_key (k): Contains key K

Dic.items (): Get a list of keys and values

Dic.keys (): Get a list of keys

Dic.pop (k): Delete key k

Dic.update (): Update member (update dictionary with another dictionary)

Dic.values (): Get a list of values

Python: The basic operation of a dictionary