25、python基础学习-集合

 1 #!/usr/bin/env python
 2 #__author: hlc
 3 #date: 2019/6/1
 4
 5 # set 集合
 6 # 集合 把不同的元素组成一起形成集合，集合时python的基础类型
 7 # 组成集合的成员不可重复
 8 # a = [1,2,3,4,5,1,2,3,4,5,"a","a","a","b","b""b","c"]
 9 # b = set(a) # 通过set关键字定义集合
10 # print(a) # [1, 2, 3, 4, 5, 1, 2, 3, 4, 5, ‘a‘, ‘a‘, ‘a‘, ‘b‘, ‘bb‘, ‘c‘]
11 # print(b) # {1, 2, 3, 4, 5, ‘a‘, ‘bb‘, ‘c‘, ‘b‘}
12
13 # 集合对象时一个无序排列的可哈希的值：集合成员可以做字典的键
14 # a = [["asdf",1244],1,2,3,4,5,1,2,3,4,5,"a","a","a","b","b""b","c"]
15 # b = set(a) # TypeError: unhashable type: ‘list‘
16 # print(b)
17
18 # 集合分类：可变集合，不可变集合
19 # 可变集合，可添加和删除元素，非可哈希，不能用作字典的键，也不能作为其他集合的元素,不可变集合与之相反
20 # a = [1,2,3]
21 # b = set(a) # TypeError: unhashable type: ‘set‘
22 # c = {b:"sdf"}
23
24 # 集合的创建
25 # 由于集合没有自己的语法格式，只能通过集合的工厂方法set()和frozenset()创建
26 # s1 = set("asfd")
27 # s2 = frozenset("dsg")
28 # print(s1,type(s1)) # {‘f‘, ‘d‘, ‘a‘, ‘s‘} <class ‘set‘>
29 # print(s2,type(s2) # frozenset({‘d‘, ‘g‘, ‘s‘}) <class ‘frozenset‘>
30
31 # 访问集合
32 # 由于集合本身是无序的，所以不能为集合创建索引或切片操作，只能循环遍历或使用in、not in来访问或判断集合元素。
33 # s1 = set("asdfsd")
34 # print("a" in s1) # True
35 # s1[0] # TypeError: ‘set‘ object is not subscriptable
36
37 # for i in s1 :
38 #     print(i)
39 # d
40 # s
41 # a
42 # f
43
44 # 更新集合，可使用以下内建方法更新：
45 # s1 = set("asdf")
46 # s1.add()
47 # s1.update()
48 # s1.remove()
49 # 只有可变集合才能更新
50 # s1 = frozenset("gdsfg")
51 # # s1.add() # AttributeError: ‘frozenset‘ object has no attribute ‘add‘
52
53 # s2 = set("sdf")
54 # # s2.add("mmn") # {‘f‘, ‘mmn‘, ‘d‘, ‘s‘}
55 # s2.update("jkl") # {‘d‘, ‘l‘, ‘s‘, ‘k‘, ‘j‘, ‘f‘}
56 # print(s2)
57
58 # s1 = set(["asdf",325,"456"])
59 # # s1.remove(325) # {‘456‘, ‘asdf‘}
60 # s1.pop() # {‘asdf‘, 325}
61 # s1.clear() # set()
62 # del s1 # NameError: name ‘s1‘ is not defined
63 # print(s1)
64
65 # 集合类型的操作符
66 # in ,not in
67 # 集合等价于不等价（==，！=）
68 # 子集 超集
69 # print(set("asd") == set("asdasd")) # True
70 # s = set("adsfas")
71 # s1 = set("ads")
72 # print("s" in s) # True
73 # print(s > s1) # True
74
75 # 联合（|） 联合（union）的操作与集合的or操作其实等价的，联合符号有个等价的方法，union（）
76 # s1 = set("qewr")
77 # s2 = set("ghkj")
78 # s3 = s1|s2
79 # print(s3) # {‘e‘, ‘k‘, ‘r‘, ‘h‘, ‘w‘, ‘g‘, ‘q‘, ‘j‘}
80 # print(s1.union(s2)) # {‘e‘, ‘k‘, ‘r‘, ‘h‘, ‘w‘, ‘g‘, ‘q‘, ‘j‘}
81
82 a = set([1,2,3,4,5])
83 b = set([4,5,6,7,8])
84
85 # 交集 intersrction（）等同于 a & b
86 # print(a.intersection(b)) # {4, 5}
87 # 并集 union 等同于 a | b
88 # print(a.union(b)) # {1, 2, 3, 4, 5, 6, 7, 8}
89 # 差集 difference 等同于a - b
90 # print(a.difference(b)) # {1, 2, 3}
91 # print(b.difference(a)) # {8, 6, 7}
92 # 对称差集（反向交集） symmetric_difference  等同于 a ^ b
93 # print(a.symmetric_difference(b)) # {1, 2, 3, 6, 7, 8}
94 # 父集，超集
95 # print(a.issuperset(b)) # >  False
96 # 子集
97 # print(a.issubset(b)) # < False

原文地址：https://www.cnblogs.com/hlc-123/p/10960311.html