在数学中，集合是不同对象的集合，这些对象本身就是对象。例如，数字2、4和6在分别考虑时是不同的对象，但是当将它们一起考虑时，它们形成一个由{2,4,6}组成的单一大小三集。
| 运作方式 | 符号 | 含义 |
|---|---|---|
| 路口 | A∩B | 同时存在的所有元素和 |
| 联盟 | A∪B | 或（或两者）中的所有元素 |
| 区别 | A − B | 所有但不在其中的所有元素 |
| 补充 | （要么） | 所有不在的元素 |
与列表相比，在python中，使用集合的主要优点是它具有优化的功能，可以检查特定元素是否为集合的成员。这基于哈希表数据结构。
add(x)方法：如果不存在项x，则将项x添加到集合中。
A = {"AA", "BB", "CC"}
A.add("VV")这将在A组中添加VV。
union(s)方法：返回两个集合的并集。在两个现有集合之间使用运算符'|'与编写My_Set1.union(My_Set2)相同。
A = {"AA", "BB", "CC"}
B = {"MM", "NN"}
Z = A.union(B)
OR
Z = A|B集人口集将具有A和B的成分。
intersect(s)方法：返回两个给定集的交集。可以在此操作中使用“＆”运算符。
S = A.intersection(B)
集合受害者将包含A和B的共同要素。
差异方法：返回一个集合，其中包含第一个集合中存在但第二个集合中不存在的所有元素。我们可以在这里使用“-”运算符。
W = A.difference(B) OR S = A – B
设置安全将具有A中的所有元素，但B中没有。
clear()方法：现有的整个集合将为空。
B.clear()
清除B套
集和冻结集支持以下运算符-
key in s # containment check key not in s # non-containment check s1 == s2 # s1 is equivalent to s2 s1 != s2 # s1 is not equivalent to s2 s1 <= s2 # s1is subset of s2 s1 < s2 # s1 is proper subset of s2 s1 >= s2 # s1is superset of s2 s1 > s2 # s1 is proper superset of s2 s1 | s2 # the union of s1 and s2 s1 & s2 # the intersection of s1 and s2 s1 – s2 # the set of elements in s1 but not s2 s1 ˆ s2 # the set of elements in precisely one of s1 or s2
# Python program to demonstrate working# of
# Set in Python
# creating two sets
My_Set1 = set()My_Set2 = set()# Adding elements to My_Set1
for i in range(1, 6):
My_Set1.add(i)
# Adding elements to My_Set2
for i in range(3, 8):
My_Set2.add(i)
print("My_Set1 = ", My_Set1)
print("My_Set2 = ", My_Set2)
print("\n")
# Union of My_Set1 and My_Set2
My_Set3 = My_Set1 | My_Set2# My_Set1.union(My_Set2)
print("Union of My_Set1&My_Set2: My_Set3 = ", My_Set3)
# Intersection of My_Set1 and My_Set2
My_Set4 = My_Set1&My_Set2# My_Set1.intersection(My_Set2)
print("Intersection of My_Set1&My_Set2: My_Set4 = ", My_Set4)
print("\n")
# Checking relation between My_Set3 and My_Set4
if My_Set3>My_Set4: # My_Set3.issuperset(My_Set4)
print("My_Set3 is superset of My_Set4")
elif My_Set3<My_Set4: # My_Set3.issubset(My_Set4)
print("My_Set3 is subset of My_Set4")
else : # My_Set3 == My_Set4
print("My_Set3 is same as My_Set4")
# displaying relation between My_Set4 and My_Set3
if My_Set4<My_Set3: # My_Set4.issubset(My_Set3)
print("My_Set4 is subset of My_Set3")
print("\n")
# difference between My_Set3 and My_Set4
My_Set5 = My_Set3 - My_Set4
print("Elements in My_Set3 and not in My_Set4: My_Set5 = ", My_Set5)
print("\n")
# check if My_Set4 and My_Set5 are disjoint sets
if My_Set4.isdisjoint(My_Set5):
print("My_Set4 and My_Set5 have nothing in common\n")
# Removing all the values of My_Set5
My_Set5.clear()
print("After applying clear on sets My_Set5: ")
print("My_Set5 = ", My_Set5)输出结果
My_Set1 = {1, 2, 3, 4, 5}
My_Set2 = {3, 4, 5, 6, 7}
Union of My_Set1&My_Set2: My_Set3 = {1, 2, 3, 4, 5, 6, 7}
Intersection of My_Set1&My_Set2: My_Set4 = {3, 4, 5}
My_Set3 is superset of My_Set4
My_Set4 is subset of My_Set3
Elements in My_Set3 and not in My_Set4: My_Set5 = {1, 2, 6, 7}
My_Set4 and My_Set5 have nothing in common
After applying clear on sets My_Set5:
My_Set5 = set()