Python notes-----dictionaries, tuple operations

1. Dictionaries

is a Key-value data type that is used like a dictionary

Unordered because there is no subscript

Create a dictionary:

info = {
' stu1 ':' QQ ',
' stu2 ':' ww ',
' stu3 ':' ee ',
}

Print(info)

Output results

{' stu1 ': ' QQ ', ' stu2 ': ' ww ', ' stu3 ': ' EE '}

1.1 Changes have been modified, there is no increase

info[ "GG"
info[ ' Sut4 ' ' hhh '
print (info)
{' stu1 ': ' GG ', ' stu2 ': ' ww ', ' stu3 ': ' ee ', ' sut4 ': ' HHH '}

1.2 DeleteDel,pop () deletes the specified

del info[' stu1 ']

Print(info)

{' STU2 ': ' ww ', ' stu3 ': ' ee ', ' sut4 ': ' HHH '}
Info.pop (' stu2 ')
Print(info)

{' stu3 ': ' ee ', ' sut4 ': ' HHH '}

Popitem () Random deletion

Info.popitem ()
Print(info)

{' stu3 ': ' EE '}

1.3 QueriesGet (' Keys ') query key, there is return value, if not, return none

Print(info.get (' stu1 '))

Qq

1.4 Dictionary NestingVALUES (), keys () query key and values

City = {
"Beijing": ["Dongcheng", "Xicheng", "Great Joy City"],
"Shanghai": ["Hongqiao", "Shanghai Zoo", "Oriental Pearl"],
"Zhejiang": ["Hangzhou", "Wenzhou", "Hengdian"],
}

#打印values
Print (City.values ())

Dict_values ([' East Side ', ' West Side ', ' Grand Hyatt City '], [' Hongqiao ', ' Shanghai Zoo ', ' Oriental Pearl '], [' Hangzhou ', ' Wenzhou ', ' Hengdian ']]

#打印key
Print (City.keys ())

Dict_keys ([' Beijing ', ' Shanghai ', ' Zhejiang '])

SetDefault () Method-Increase

City.setdefault ("USA", {"United States": ["Washington", "Los Angeles", "Universal Studios"]})

Print (city)

{' Beijing ': [' Dongcheng ', ' Xicheng ', ' Grand Yue City ', ' Shanghai ': [' Hongqiao ', ' Shanghai Zoo ', ' Oriental Pearl '], ' Zhejiang ': [' Hangzhou ', ' ' Wenzhou ', ' Hengdian '], ' USA ': {' USA ': [' Washington ', ' Los Angeles ', ' Universal Studios ']} }

Dir1.update (DIR2) update

info = {
' STU1 ': ' QQ ',
' STU2 ': ' WW ',
' Stu3 ': ' ee ',
}
b = {
' STU1 ': ' Qwe ',
1:3,
2:5,
}
Info.update (b)
Print (info)

{' stu1 ': ' qwe ', ' stu2 ': ' ww ', ' stu3 ': ' ee ', 1:3, 2:5}

The items () dictionary is turned into a list

Print (Info.items ())

Dict_items ([' stu1 ', ' QQ '), (' Stu2 ', ' ww '), (' Stu3 ', ' ee ')])

Fromkeys ([1], "str") Initializes a new dictionary, each value is assigned the same

Print (Dict.fromkeys ([6,7,8], "Yrdy"))

{6: ' Yrdy ', 7: ' Yrdy ', 8: ' Yrdy '}

Modify the dictionary initialized with Fromkeys one layer, will follow the change

c = dict.fromkeys ([6,7,8] ,[1,{ "Name" : "wsy" }, 555 print (c)
C[7 ][1][ ' name ' ] = Span lang= "en-us" > "Jack"
print (c)

{6: [1, {' name ': ' Wsy '}, 555], 7: [1, {' name ': ' Wsy '}, 555], 8: [1, {' name ': ' Wsy '}, 555]}

{6: [1, {' name ': ' Jack '}, 555], 7: [1, {' name ': ' Jack '}, 555], 8: [1, {' name ': ' Jack '}, 555]}

1.5 Cycle of the dictionary

City = {
"Beijing": ["Dongcheng", "Xicheng", "Great Joy City"],
"Shanghai": ["Hongqiao", "Shanghai Zoo", "Oriental Pearl"],
"Zhejiang": ["Hangzhou", "Wenzhou", "Hengdian"],
}

For I in the city : #高效
print (I,city[i])

For v,k in City.items (): #低效
print (v,k)

Beijing [' Dongcheng ', ' Xicheng ', ' Great Joy City ']
Shanghai [' Hongqiao ', ' Shanghai Zoo ', ' Oriental Pearl ']
zhejiang [' Hangzhou ', ' Wenzhou ', ' Hengdian ']

2. Tuples

can only check

List tuples convert to each other

names = ("wsy","wwsy","Jack" )
p = list(names)
Print(p)

[' Wsy ', ' wwsy ', ' Jack ']

Convert back

names = ("wsy","wwsy","Jack" )
p = list(names)
q = tuple(p)
Print(q)

(' wsy ', ' wwsy ', ' Jack ')

Index method-Returns the index position subscript

Names = ("wsy","Wwsy","Jack")
p = Names.index ("Jack")
Print(p)

2

Count Method-Search for characters, return number

Names = ("wsy","Wwsy","Jack")
p = names.count ("wsy")
Print(p)

1

3. CollectionThe collection contains only numbers

List_1 = [1,4,5,7,3,6,7,9]
Print (list_1)
List_1 = Set (list_1)
List_2 =set ([2,6,0,66,22,8,4])
Print (list_1,list_2)

[1, 4, 5, 7, 3, 6, 7, 9]
{1, 3, 4, 5, 6, 7, 9} {0, 2, 66, 4, 6, 8, 22}

Intersection () method-Finding the intersection

Print (List_1.intersection (list_2))
Print (List_1 & list_2)

Union () Method-Set

Print (List_1.union (list_2))
Print (list_2 | list_1)

Difference () Method-seeking difference Set

#差集 in list_1 and not in list_2
Print (List_1.difference (list_2))
Print (List_2.difference (list_1))

Determine if it is a subset

List_3 = Set ([1,3,7])
Print (List_3.issubset (list_1))
Print (List_1.issuperset (list_3))

Symmetric_difference () method to find symmetric difference sets

Print (List_1.symmetric_difference (list_2))

Print (list_1 ^ list_2)

Pop () method random Delete

Print (List_1.pop ())

Python notes-----dictionaries, tuple operations