python collection

set features: the different elements together, the element hash value must be immutable

Create a set of

SET = S ( 'Alex Li') 
Print (S) 

forms; deduplication    
{ 'e', 'i' , '', 'l', 'a', 'x'}

to re-set collection

and = [ 'CX', 'chenxi' 'CX'] 
print () 
print (set ()) 


[ 'CX', 'chenxi' 'CX'] 
{chenxi '' CX '}

　　to re-set and view the data type

and = [ 'CX', 'chenxi' 'CX'] 
print () 
print (set (and) type (set ())) 




{ 'i', 'a', 'e', 'x' , '', 'l'} 
'CX', 'chenxi' 'CX'] 
{chenxi '' CX '} <class' set ''

　　set of different combinations of elements together, but the element must not change

li = [[1,2],3,'tyuio']
a = set(li)
print(a)



Traceback (most recent call last):
  File "D:/python/map.py", line 308, in <module>
    a = set(li)
TypeError: unhashable type: 'list'

　　set collection is divided into a set of variable and non-variable collection; creation mode

s1 = set('alvin')   # 可变

s2 = frozenset('yuan')   #不可变
print(s1,type(s1))
print(s2,type(s2))



测试
{'i', 'v', 'l', 'a', 'n'} <class 'set'>
frozenset({'n', 'y', 'u', 'a'}) <class 'frozenset'>

　　Access to the collection of collections to determine whether there exists an element

S1 = SET ( 'Alvin') 
Print ( 'a' in S1) # determines a element exists in the collection; presence of Ture, absent False 
Print ( 'B' in S1) 
for I in S1: 
    Print (I) 




true 
False 
A 
L 
n- 
I 
V

　　The collection add a single element

def df (): # view the content of the element function 
    # print ( 'a' in s1 ) # determines a element exists in the collection; presence of Ture, False absence 
    # Print ( 'B' in S1) 
    Print ( "* ******************************* ") 
    for I in S1: 
        Print (I) 
    Print ( '\ n---- ------ \ n-') 

a = [1,5,2, "wertayuio", 6,5] 
S1 = SET (a) 
DF () 
s1.add ( "WSD") added to the element in a # element 
DF () 



False 
False 
******************************** 
. 1 
2 
wertayuio 
. 5 
. 6 
------- - 
False 
False 
******************************** 
. 1 
wertayuio 
. 5 
. 6 
---------

　　Update (add more elements) elements

s1.update ( "ops2") # additive element as a sequence, if repeated, add only one 
DF () 
. 1 
2 
. 5 
. 6 
wertayuio 
--------- 

. 1 
2 
. 5 
. 6 
P 
wertayuio 
O 
S 
2 
---- -----

　　Update (add more elements) elements

s1.update ([12, 'wwww' ]) # If the list update only add two 
DF () 





Test 
D: \ pyth \ python.exe D: /python/map.py 
wertayuio 
. 1 
2 
. 5 
. 6 
----- ---- 

wertayuio 
. 1 
2 
. 5 
. 6 
12 is 
of wwww 
---------

　　Delete the specified set of operating elements

s1.remove (2) # delete the specified operation element 
DF () 



. 1 
2 
. 5 
. 6 
wertayuio 
--------- 

. 1 
. 5 
. 6 
wertayuio 
---------

　　Random deletion

Print (S1) 
s1.pop () 
Print (S1) 



testing 
{. 1, 2,. 5,. 6, 'wertayuio'} 
{2,. 5,. 6, 'wertayuio'}

　　Empty the contents of the collection

print(s1)
s1.clear()  #清空
print(s1)

{1, 2, 'wertayuio', 5, 6}
set()

　　Determining whether a set of two identical

SET = S ( "Chenxi") 
S1 = SET ( "chenxixi") 
Print (S == S1) # determines whether the two sets are equal, equal to True 




True

　　Determining whether the set is a set comprising 2

print (set ( "qwert") <set ( "qwertyuiop")) # determines which collection contains former 



True

　　Collection and with or

print (set ( "12345") or set ( "567890")) # print set The previous set of 
print (set ( "12345") and set ( "567890")) # print set behind 



{ '2', '4 ',' 5 ',' 1 ',' 3 '} 
{' 8 ',' 0 ',' 5 ',' 6 ',' 9 ',' 7 '}

　　Intersection of the sets with union

SET = S1 ( "123456") 
S2 = SET ( "456789") 
Print (s2.intersection (S1)) # intersected; two set of elements common to 
print (s2.union (s1)) # fetch and set, indicating take the set of all elements and two deduplication

print (s1 | s2) and find another method set # 

{ '5', '4', '6'}

{'7', '8', '5', '3', '2', '4', '1', '9', '6'}

{'7', '8', '5', '3', '2', '4', '1', '9', '6'}

　　Taking the difference-set of Assembly

SET = s1 ( "123456") 
s2 = SET ( "456789") 

Print (s2.difference (s1)) # s2 taken in some, s1 there are no elements in 

print (s1.difference (s2)) # s1 taken in some, s2 there are no elements

print (s1.symmetric_difference (s2)) # take the symmetric difference

{'7', '8', '9'}
{'1', '3', '2'}
{'7', '1', '9', '2', '8', '3'}

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