Python Create and Access dictionaries

>>> Dict1 = {' A ': ' 1 ', ' B ': ' 2 ', ' C ': ' 3 ', ' d ': ' 4 '}

>>> print (' A's value is: ', dict1[' a '])

The value of a is: 1

>>> Dict4 = dict (' I ' = ' happy ', you = ' sadness ')

Syntaxerror:keyword can ' t be an expression

>>> dict4[' you '] = ' change sadness '

>>> Dict4

{' I ': ' Happy ', ' you ': ' Change Sadness '}

>>> dict4[' he '] = ' Add one '

>>> Dict4

{' I ': ' Happy ', ' you ': ' Change sadness ', ' he ': ' Add one '}

Fromkeys (S[,v]) creates and returns a new dictionary

>>> Dict1 = {}

>>> Dict1.fromkeys ((+))

{1:none, 2:none, 3:none}

>>> Dict1.fromkeys ((+), ' num ')

{1: ' num ', 2: ' Num ', 3: ' Num '}

>>> Dict1.fromkeys ((1,3), ' number ') # If you want to change the value of the key with Fromkeys, the new dictionary will not be created successfully

{1: ' Number ', 3: ' Number '}

Ways to access a dictionary

Keys ()

VALUES ()

Items ()

>>> dict2 = {}

>>> Dict2 = Dict2.fromkeys (range (2), ' the ' only ')

>>> Dict2

{0: ' the ' ", 1: ' The '"}

>>> for Eachkey in Dict2. keys (): #values as ' an '

Print (Eachkey)

0

1

>>> for Eachitem in Dict2. items ():

Print (Eachitem)

(0, ' a few ')

(1, ' a few ')

Get () Find Method

>>> Dict2 = Dict2.fromkeys (range (10), ' the ' only ')

>>> Dict2

{0: ' A few ', 1: ' The ', ' 2: ' The ', ' 3: ' The ', ' 4: ' The ', ' 5: ' The ', ' 6: ' The ', ' 7

>>> dict2.get (5, ' none ') #如果有则返回值, if not, return ' none '

' A few '

>>> Dict2.get (10, ' none ')

No

>>> 5 in Dict2 #成员操作符判定

True

>>> in Dict2

False

Clean () Empty A dictionary

>>> Dict2.fromkeys (Range (1), ' happy ')

{0: ' Happy '}

>>> Dict2.clear ()

>>> Dict2

{}

Copy ()

>>> a = {1: ' One ', 2: ' One ', 3: ' Three ', 4: ' Four '}

>>> A

{1: ' One ', 2: ' Both ', 3: ' Three ', 4: ' Four '}

>>> B = a.copy ()

>>> C = A

>>> b

{1: ' One ', 2: ' Both ', 3: ' Three ', 4: ' Four '}

>>> C

{1: ' One ', 2: ' Both ', 3: ' Three ', 4: ' Four '}

>>>

>>> c[5] = ' five '

>>> C

{1: ' One ', 2: ' Both ', 3: ' Three ', 4: ' Four ', 5: ' Five '}

>>> A

{1: ' One ', 2: ' Both ', 3: ' Three ', 4: ' Four ', 5: ' Five '}

>>> b

{1: ' One ', 2: ' Both ', 3: ' Three ', 4: ' Four '}

Pop ()

Popitem () Random Popup

>>> A.pop (2)

' Both '

>>> A

{1: ' One ', 3: ' Three ', 4: ' Four ', 5: ' Five '}

>>> A.popitem ()

(5, ' five ')

>>> A

{1: ' One ', 3: ' Three ', 4: ' Four '}

>>> A.setdefault(7, ' seven ')

' Seven '

>>> A

{1: ' One ', 3: ' Three ', 4: ' Four ', 7: ' Seven '}

>>> B = {7: ' SEVEN '}

>>> A

{1: ' One ', 3: ' Three ', 4: ' Four ', 7: ' Seven '}

>>> A.update (b)

>>> A

{1: ' One ', 3: ' Three ', 4: ' Four ', 7: ' SEVEN '}

Python Create and Access dictionaries