Python set set type operation summary

In addition to dictionaries, lists, and tuples, there is a very useful data structure in Python, which is set. If you use set flexibly, you can subtract a lot of operations (although set can be replaced by lists).

Small example

1. If I want to find the same item in many lists, it is best to use sets

x & y & z #  intersection 

2. To weight

>>> lst = [1,2,3,4,1]

>>> print list(set(lst))

[1, 2, 3, 4]

usage

Notice that set doesn't have the concept of position so the list method doesn't slice anything, it's converted to list when it's needed, okay

The built-in function creates a set

set([1, 2, 3, 4])

Basic operation

t.add('x')            #  To add a 

s.update([10,37,42])  #  in s Add multiple items in 
t.remove('H') #  To delete a 
len(s)  # set  The length of the 
x in s #  test  x  Whether it is  s  A member of the  
x not in s   #  test  x  If not  s  A member of the  
s.issubset(t)  

s <= t  #  To test whether  s  Each of the elements in  t  In the  
s.issuperset(t)  

s >= t  #  To test whether  t  Each of the elements in  s  In the  
s.union(t)  

s | t  #  Return a new  set  contains  s  and  t  Each of the elements  
s.intersection(t)  

s & t  #  Return a new  set  contains  s  and  t  Public elements in  
s.difference(t)  

s - t  #  Return a new  set  contains  s  There is however,  t  Elements that are not in  
s.symmetric_difference(t)  

s ^ t  #  Return a new  set  contains  s  and  t  The element that does not repeat  
s.copy()  #  return  set  " s A shallow copy of