How to use multiple key values and repeated key values in python dictionary (detailed explanation)

Use a dictionary in Python, the format is as follows:

dict={ key1:value1 , key2;value2 ...}

The format used when actually accessing dictionary values ​​is as follows:

dict[key]

Multi-key

The multi-key form of the dictionary is as follows:

dict={(ke11,key12)：value ，(key21,key22):value ...}

The specific form when actually accessing the value in the dictionary is as follows (take the first key as an example):

dict[key11,key12]

or:

dict[(key11,key12)]

The following is a practical example:

Multivalued

When a key value corresponds to multiple values, the format:

dict={key1:(value1,value2 ..), key2:(value1,value2 ...) ...}

The format for accessing the values ​​in the dictionary is as follows:

dict[key]

or

dict[key][index]

Loop assignment (emphasis)

The syntax structure is shown in the following example

to sum up:

Through the above description, we can know that in the definition of the dictionary, the colon (:) before and after the sign is a whole respectively, that is, use parentheses () to include the parts before and after the colon respectively. When accessing the dictionary value, it is best to put the key Become a whole in parentheses.

Multiple key-value pairs with the same key-value

That is, in the dictionary, there are at least two members whose keys are the same, but the values ​​corresponding to the keys are different. The format is as follows:

dict={ key1: value1
key1: vaklue2,
... }

In this form, the value assigned to the key later becomes the true value of the key.

Use lists and dictionaries as dictionary values

format

dict={ key1:(key11:value,key12:value) ,
key2:(key21:value,key22:value)
}

Access dictionary value format (take the first key as an example):

dict[key1][key11]

The actual example is as follows:

#encoding=utf-8

print '中国'

#字典的一键多值

print'方案一 list作为dict的值 值允许重复'

d1={}
key=1
value=2
d1.setdefault(key,[]).append(value)
value=2
d1.setdefault(key,[]).append(value)

print d1

#获取值
print '方案一 获取值'
print list(d1[key])

print '方案一 删除值，会留下一个空列表'
d1[key].remove(value)
d1[key].remove(value)
print d1

print '方案一 检查是否还有一个值'
print d1.get(key,[])

print '方案二 使用子字典作为dict的值 值不允许重复'

d1={}
key=1
keyin=2
value=11
d1.setdefault(key,{})[keyin]=value
keyin=2
value=22
d1.setdefault(key,{})[keyin]=value
keyin=3
value=33
d1.setdefault(key,{})[keyin]=value

print d1

print '方案二 获取值'
print list(d1[key])

print '方案二 删除值，会留下一个空列表'
del d1[key][keyin]
keyin=2
del d1[key][keyin]
print d1

print '方案二 检查是否还有一个值'
print d1.get(key,())

print '方案三 使用set作为dict的值 值不允许重复'
d1={}
key=1
value=2
d1.setdefault(key,set()).add(value)
value=2
d1.setdefault(key,set()).add(value)
value=3
d1.setdefault(key,set()).add(value)

print d1

print '方案三 获取值'
print list(d1[key])

print '方案三 删除值，会留下一个空列表'
d1[key].remove(value)
value=2
d1[key].remove(value)
print d1

print '方案三 检查是否还有一个值'
print d1.get(key,())

 

Print result:

China
Option 1 list as the value of dict allows repeating
{1: [2, 2]}

Get the value
[2, 2] and
delete the value, leaving an empty list
{1: []} to
check if there is another value
[]

方案二 使用子字典作为dict的值 值不允许重复
{1: {2: 22, 3: 33}}
获取值
[2, 3]
删除值，会留下一个空列表
{1: {}}
检查是否还有一个值
{}

方案三 使用set作为dict的值 值不允许重复
{1: set([2, 3])}
获取值
[2, 3]
删除值，会留下一个空列表
{1: set([])}
检查是否还有一个值
set([])