集合基础用法

# 集合



# 关系运算
# 1.作用
# 1.1 关系运算 寻找共同好友 for循环 此种方式比较麻烦
from re import M, S




my_friends = ["egon","tom","jason"]
his_friends = ["egon","tom","jack"]
l=[]
for x in my_friends:
    if x in his_friends:
        l.append(x)
print(l)



'''
2. 定义：在{}内用逗号分隔开多个元素，多个元素需要满足以下三个条件
    1.集合内元素必须为不可变类型
    2.集合内元素无序
    3.集合内元素没有重复



    定义空集合 a=set()
    a={} 类型为字典
'''
a= {1,2,3,4,5,1,'list','sb'}
print(type(a),a)



# 3.类型转换
a = set('hello world')
print(a)



# 4.内置方法
my_friends = {"egon","tom","jason"}
his_friends = {"egon","tom","jack"}
# 4.1 取交集：取两者共同的好友
togither_friends = my_friends & his_friends
print(togither_friends)
print(my_friends.intersection(his_friends)) # 内置函数
# # 4.2 取合集 ：两者共同的好友
togither_friends = my_friends | his_friends
print(togither_friends)
print(my_friends.union(his_friends))



# # 4.3 取my_friends共同的好友
print(my_friends-his_friends)
print(my_friends.difference(his_friends))



# # 取his_friends共同的好友
print(his_friends-my_friends)
print(my_friends.difference(his_friends))



# 4.4 对称差集：求两个用户独有的好友们
print(my_friends ^ his_friends)
print(my_friends.symmetric_difference(his_friends))



# 4.5 父子集：包含关系
s1 = {1,2,3}
s2 = {1,2}
print(s1>s2) # 当s1大于或等于s2时，才能说s1是s2的爹
print(s1.issuperset(s2))



# s1 = {1,2,3}
# s2 = {1,2,3}
# print(s1==s2) # 当s1=s2时，互为父子




'''
 去重
 1.只能对不可变类型去重
 2.无法保证原来的顺序
 所以我们基本不会用集合去重
'''
l=[
    {'name':'wangxue','age':18,'sex':'male'},
    {'name':'wangjing','age':28,'sex':'male'},
    {'name':'bob','age':38,'sex':'female'},
    {'name':'wangxue','age':18,'sex':'male'},
]
new_l = []
for k in l:
    if k not in new_l:
        new_l.append(k)
print(new_l)



# discard和remove区别 discard：删除一个不存在的元素不会报错，容错性更好
s = {1,2,3}
s.discard(4)
# s.remove(4)
print(s)



# update追加
s.update({1,3,4,'hello'})
print(s)