python-Collection (SET)

                                    Collection

A collection is an unordered, non-repeating collection of data in which the elements are hashed (immutable types), but the collection itself is not hashed (so the collection cannot be a key to the dictionary). The following are the two most important points of the collection:
Go to the weight, turn a list into a set, and automatically go heavy.
Relationship test, test the intersection of two sets of data, difference set, and the relationship between the set.

# The elements inside the collection are hashed

# Set1 = {' 1 ', ' Alex ', 2,true,[1,2,3]}  #报错 #  set2 = {' 1 ', ' Alex ', 2,true,{1:2}}  #报错  #  set3 = {' 1 ', ' Alex ', 2,true, (1,2,[2,3,4])}  #报错

Go heavy

# l= [1,1,2,2,3,4,5,5] # Set1 = set (l) # Print (Set1,type (SET1)) # L = List (Set1) # Print (L,type (l))

Creation of collections

# Set1 = Set ({A-st, ' Barry '}) # Set2 = {, ' Barry '} # Print (Set1,type (SET1)) # Print (Set2,type (Set2))

Increase

# Set1 = {' Alex ', ' Wusir ', ' Ritian ', ' Egon ', ' Barry '} # set1.add (' Wen ') # print (Set1) # Update: Iterate increments # set1.update (' A ') # print (Set1) # set1.update (' teacher ') # print (Set1) # set1.update ([i]) # print (Set1)

By deleting

#set = {' Alex ', ' Wusir ', ' Ritian ', ' Egon ', ' Barry '}#set.remove (' Alex ') #删除一个元素#print (set)#Random Pop deletion#Set.pop () #随机删除一个元素#print (set)#Clear Clear#set.clear () #清空集合#print (set)#del#del set #删除集合#print (set)

Other operations of the collection

#1. Intersection (& or intersection)#Set1 = {1,2,3,4,5}#Set2 = {4,5,6,7,8}#print (Set1&set2) #-->{4, 5}#Print (Set1.intersection (Set2))#2. Union (| or unions)#Set1 = {1,2,3,4,5}#Set2 = {4,5,6,7,8}#Print (Set1 | set2) #-->{1, 2, 3, 4, 5, 6, 7, 8}#Print (Set1.union (Set2)) #-->{1, 2, 3, 4, 5, 6, 7, 8}#3. Difference set (-or difference)#Set1 = {1,2,3,4,5}#Set2 = {4,5,6,7,8}#print (Set1-set2)#Print (Set1.difference (Set2)) #-->{1, 2, 3}#4. Inverse intersection (^ or symmetric_difference)#Set1 = {1,2,3,4,5}#Set2 = {4,5,6,7,8}#Print (set1 ^ set2) #-->{1, 2, 3, 6, 7, 8}#Print (Set1.symmetric_difference (Set2))#5 subsets and hyper-sets#Set1 = { A-i}#Set2 = {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, both of which illustrate that Set2 is a set1 superset. 

Frozenset the immutable collection, making the collection immutable.

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

Shallow copy

 #   L1 = [1,2,3,[' Barry ', ' Alex ']]  #   L2 = L1  ##  Span style= "COLOR: #008000" > l1[0] = 111  #   Print (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 ']]  #   print (ID (L1), id (L2)) #- --for assignment operations, L1 and L2 point to the same memory address, so they are exactly the same. 
  

# li = [1,2,3,[' Barry ', ' Alex ']
# L2 = Li.copy ()
# Print (Li,id (LI))
# Print (L2,id (L2))
# Li[1] = 222
# Print (Li,id (LI))
# Print (L2,id (L2))
# Li[3][0] = ' Wusir '
# Print (Li,id (li[3))
# Print (L2,id (l2[3))
# for shallow copy, the first layer creates a new memory address, and starting at the second level, it points to the same memory address.
# So, for the second and deeper layers, maintain consistency

# deep Copy Deepcopy

#Import Copy#li = [1,2,3,[' Barry ', ' Alex ']#L2 = Copy.deepcopy (li)#print (Li,id (LI))#Print (L2,id (L2))##li[1] = 222#print (Li,id (LI))#Print (L2,id (L2))##li[3][0] = ' Wusir '#Print (Li,id (li[3) )#Print (L2,id (l2[3) )#for deep Copy, the two are completely antagonistic, changing any element of any one (no matter how many layers), and the other absolutely does not change

python-Collection (set)