set集合，是一个无序且不重复的元素集合

一、集合的创建：

set1={1,2,‘barry‘}
set2={1,2,‘barry‘}
print(set1,set2)
#{1, 2, ‘barry‘} {1, 2, ‘barry‘}

2、集合的增

add

set1={‘alex‘,‘wusir‘,‘ritian‘,‘egon‘,‘barry‘}
set1.add(‘taibai‘)
print(set1)
#{‘taibai‘, ‘wusir‘, ‘ritian‘, ‘alex‘, ‘barry‘, ‘egon‘}

update()：在对集合增加元素的时候是迭代增加到集合中的。

set1={‘alex‘,‘wusir‘,‘ritian‘,‘egon‘,‘barry‘}
set1.add(‘taibai‘)
set1.update(‘A‘)
print(set1)
#{‘egon‘, ‘alex‘, ‘taibai‘, ‘wusir‘, ‘barry‘, ‘A‘, ‘ritian‘}
set1.update(‘老师‘)
print(set1)
#{‘师‘, ‘ritian‘, ‘A‘, ‘老‘, ‘egon‘, ‘taibai‘, ‘wusir‘, ‘alex‘, ‘barry‘}
set1.update([1,2,3])
print(set1)
#{‘alex‘, ‘A‘, 1, 2, ‘ritian‘, 3, ‘师‘, ‘老‘, ‘taibai‘, ‘egon‘, ‘barry‘, ‘wusir‘}

3、集合的删

set1={‘alex‘,‘wusir‘,‘ritian‘,‘egon‘,‘barry‘}
set1.remove(‘alex‘)  # 删除一个元素
print(set1)

#{‘wusir‘, ‘ritian‘, ‘egon‘, ‘barry‘}

set1={‘alex‘,‘wusir‘,‘ritian‘,‘egon‘,‘barry‘}
set1.pop()  # 随机删除一个元素
print(set1)

#{‘egon‘, ‘alex‘, ‘wusir‘, ‘ritian‘}

set1={‘alex‘,‘wusir‘,‘ritian‘,‘egon‘,‘barry‘}
set1.clear()  # 清空集合
print(set1)

# set()

set1={‘alex‘,‘wusir‘,‘ritian‘,‘egon‘,‘barry‘}
del set1  # 清空集合
print(set1)

# Traceback (most recent call last):
#   File "C:/Pythonbc/课堂/作业讲解7.py", line 112, in <module>
#     print(set1)
# NameError: name ‘set1‘ is not defined


#这是由于使用del删除集合set1之后，set1已经不存在了，所以系统找不到会报错

二、集合的其他操作

1、交集。(&或者intersection)

set1={1,2,3,4,5}
set2={3,4,5,6,7}
print(set1 & set2)
print(set2.intersection(set1))

# {3, 4, 5}
# {3, 4, 5}

2、并集。(|或者union)

set1={1,2,3,4,5}
set2={3,4,5,6,7}
print(set1 | set2)
print(set1.union(set2))

# {1, 2, 3, 4, 5, 6, 7}
# {1, 2, 3, 4, 5, 6, 7}

3、反交集。(^或者symmetric_difference)

set1={1,2,3,4,5}
set2={3,4,5,6,7}
print(set1 ^ set2)
print(set2.symmetric_difference(set1))

# {1, 2, 6, 7}
# {1, 2, 6, 7}

4、差集。(-或者difference)

set1={1,2,3,4,5}
set2={3,4,5,6,7}
print(set1 - set2)
print(set2.difference(set1))

# {1, 2}
# {6, 7}

5、子集与超集

set1={1,2,3}
set2={1,2,3,4,6,5}
print(set1<set2)  # True
print(set1.issubset(set2))  # True
#这两个都是说明set1是set2的子集
print(set2>set1)  # True
print(set2.issuperset(set1))  # True
print(set1>set2)  # False
print(set1.issuperset(set2))  # False
#这几个说明只有当set1中所有的元素都存在于set2中时结果才为真

三、frozense不可变集合，让集合变成不可变类型。

a=frozenset(‘barry‘)
print(a,type(a))

#frozenset({‘r‘, ‘a‘, ‘y‘, ‘b‘}) <class ‘frozenset‘>