Python path-collection and depth copy

Supplemental: ID Query memory address

Print (ID (name))

is to determine the memory address int str small Data pool

int:-5-256

STR: If the string is made up of letters, it points to a memory address.

If the number is multiplied by STR (a single letter), the same memory address is within 20 (including 20).

Other data types do not have a small data pool concept.

English: str conversion bytes Str.encode (' Utf-8 ')

One, set.

The ① collection is an unordered, non-repeating collection of data.

② The elements inside it are hashed (immutable types), but the collection itself is non-hash int,str,bool () (so the collection does not have a dictionary key).

③ Collection cannot change the elements inside

④ sets can be used to find the intersection, the set, the difference set, the inverse intersection and so on.

Go weight:

1.1 Use algorithm to do.

1.2 Convert to a set, then convert it over.

When you turn a list into a collection, it automatically goes heavy.

1, creation of the collection.

Set1 = Set ({,'Barry' = {,'Barry'} Print (Set1,set2)  # {1, 2, ' Barry '} {1, 2, ' Barry '}

2, the increase of the collection.

Set1 = {'Alex','Wusir','Ritian','Egon','Barry'}set1.add ('King Goddess')Print(Set1)#Update: Iterate incrementsSet1.update ('A')Print(Set1) set1.update ('Teacher')Print(Set1) set1.update ([The])Print(Set1)

3, delete the collection.

Et1 = {'Alex','Wusir','Ritian','Egon','Barry'}set1.remove ('Alex')#Delete an elementPrint(Set1) set1.pop ()#random deletion of an elementPrint(Set1) set1.clear ()#emptying the collectionPrint(Set1)delSet1#Delete CollectionPrint(Set1)

4, the collection of check.

For ... in set

Print (..)

5, the other operations of the collection 5.1 intersect. (& or intersection)

Set1 = {1,2,3,4,5= {4,5,6,7,8}print(Set1 & Set2)  #  {4, 5}  Print(set1.intersection (Set2))  #  {4, 5}

5.2 and set. (| or union)

Set1 = {1,2,3,4,5= {4,5,6,7,8}print(Set1 | set2)  #  {1, 2, 3, 4, 5, 6, 7}print(set2.union (Set1))  #  {1, 2, 3, 4, 5, 6, 7}

5.3 Difference set. (-or diference)

Set1 = {1,2,3,4,5= {4,5,6,7,8}print(Set1-set2)  #  {1, 2, 3}Print (Set1.difference (Set2))  #  {1, 2, 3}

5.4 Inverse intersection. (^ or symmetric_difference)

Set1 = {1,2,3,4,5= {4,5,6,7,8}print(set1 ^ set2)  #  {1, 2, 3, 6, 7, 8}print(set1.symmetric_difference (Set2))  #  {1, 2, 3, 6, 7, 8}

5.5 Subsets and hyper-sets

Set1 = {= = {1,2,3,4,5,6}print(Set1 < set2)print(Set1.issubset ( Set2)  #  These two are the same, both of which illustrate that Set1 is a subset of Set2.  Print(Set2 > set1)print(Set2.issuperset (Set1))  #  These two are the same, It is the description Set2 is Set1 superset. 

6. Frozenset immutable collection to make the collection immutable.

s = Frozenset ('Barry')print(S,type (s))  #  frozenset ( {' A ', ' Y ', ' B ', ' R '}) <class ' Frozenset ' >

2, the depth copy1, first look at the assignment operation.

L1 = [1,2,3,['Barry','Alex']]l2=L1l1[0]= 111Print(L1)#[111, 2, 3, [' Barry ', ' Alex ']Print(L2)#[111, 2, 3, [' Barry ', ' Alex ']l1[3][0] ='Wusir'Print(L1)#[111, 2, 3, [' Wusir ', ' Alex ']Print(L2)#[111, 2, 3, [' Wusir ', ' Alex ']

For an assignment operation, L1 and L2 point to the same memory address, so they are exactly the same.

2, shallow copy (copy)

L1 = [1,2,3,['Barry','Alex']]l2=l1.copy ()Print(L1,id (L1))#[1, 2, 3, [' Barry ', ' Alex ']] 2380296895816Print(L2,id (L2))#[1, 2, 3, [' Barry ', ' Alex ']] 2380296895048L1[1] = 222Print(L1,id (L1))#[1, 222, 3, [' Barry ', ' Alex ']] 2593038941128Print(L2,id (L2))#[1, 2, 3, [' Barry ', ' Alex ']] 2593038941896l1[3][0] ='Wusir'Print(L1,id (l1[3]))#[1, 2, 3, [' Wusir ', ' Alex ']] 1732315659016Print(L2,id (l2[3]))#[1, 2, 3, [' Wusir ', ' Alex ']] 1732315659016

For shallow copy, the first talented woman is a separate memory address, starting from the second layer, all point to the same memory address, a change is changed.

3, deep copy

ImportCOPYL1= [1,2,3,['Barry','Alex']]l2=copy.deepcopy (L1)Print(L1,id (L1))#[1, 2, 3, [' Barry ', ' Alex ']] 2915377167816Print(L2,id (L2))#[1, 2, 3, [' Barry ', ' Alex ']] 2915377167048l1[1] = 222Print(L1,id (L1))#[1, 222, 3, [' Barry ', ' Alex ']] 2915377167816Print(L2,id (L2))#[1, 2, 3, [' Barry ', ' Alex ']] 2915377167048l1[3][0] ='Wusir'Print(L1,id (l1[3]))#[1, 222, 3, [' Wusir ', ' Alex ']] 2915377167240Print(L2,id (l2[3]))#[1, 2, 3, [' Barry ', ' Alex ']] 2915377167304

For deep copy, no matter how many layers, there are two separate memory addresses in memory.

Python path-collection and depth copy