Python集合之set和frozenset的使用详解

a = {1, 2, 3}  # 花括号内用逗号分隔
b = {i for i in range(4) if i > 0}  # 集合推导式
c = set([1, 2, 3])  # 类型构造器
print(a, type(a))
print(b, type(b))
print(c, type(c))
# {1, 2, 3} <class 'set'>
# {1, 2, 3} <class 'set'>
# {1, 2, 3} <class 'set'>

a = {1, 2, 3}
print(len(a))  # 元素数量
print(1 in a)  # 检测成员
print(1 not in a)  # 检测成员
# 3
# True
# False

A = {1, 2, 3}
B = {3, 4, 5}

print(A.intersection(B))  # 交集
print(A.union(B))  # 并集
print(A.difference(B))  # 差集
print(A.symmetric_difference(B))  # 对称差集
# {3}
# {1, 2, 3, 4, 5}
# {1, 2}
# {1, 2, 4, 5}

A = {1, 2, 3}
B = {3, 4, 5}
C = {1, 2, 3, 4, 5, 6}
D = {7, 8, 9}

# 是否无交集
print(A.isdisjoint(A))  # False
print(A.isdisjoint(B))  # False
print(A.isdisjoint(C))  # False
print(A.isdisjoint(D))  # True
print()

# 是否子集
print(A.issubset(A))  # True
print(A.issubset(B))  # False
print(A.issubset(C))  # True
print(A.issubset(D))  # False
print()

# 是否超集
print(C.issuperset(A))  # True
print(C.issuperset(B))  # True
print(C.issuperset(C))  # True
print(C.issuperset(D))  # False

A = {1, 2, 3}
B = {3, 4, 5}
C = {1, 2, 3, 4, 5, 6}
D = {7, 8, 9}

# 子集，相当于issubset(other)
print(A <= C)  # True
print(B <= C)  # True
print(C <= C)  # True
print(D <= C)  # False
print()

# 真子集
print(A < C)  # True
print(B < C)  # True
print(C < C)  # False
print(D < C)  # False
print()

# 超集，相当于issuperset(other)
print(C >= A)  # True
print(C >= B)  # True
print(C >= C)  # True
print(C >= D)  # False
print()

# 真超集
print(C > A)  # True
print(C > B)  # True
print(C > C)  # False
print(C > D)  # False
print()

# 交集，相当于intersection(*other)
print(A & B)  # {3}
print(A.intersection(B))  # {3}

# 并集，相当于union(*other)
print(A | B)  # {1, 2, 3, 4, 5}
print(A.union(B))  # {1, 2, 3, 4, 5}

# 差集，相当于difference(*other)
print(A - B)  # {1, 2}
print(A.difference(B))  # {1, 2}

# 对称差集，相当于symmetric_difference(other)
print(A ^ B)  # {1, 2, 4, 5}
print(A.symmetric_difference(B))  # {1, 2, 4, 5}

A = {1, 2, 3}
A.add(4)  # 添加单个元素
print(A)  # {1, 2, 3, 4}

A = {1, 2, 3}
A.remove(3)  # 移除单个元素，如果不存在报错
print(A)  # {1, 2}

A = {1, 2, 3}
A.discard(3)  # 移除单个元素，如果存在
A.discard(99)  # 移除单个元素，如果存在
print(A)  # {1, 2}

A = {2, 1, 3}
print(A.pop())  # 移除并返回任一元素，集合为空报错

A = {1, 2, 3}
A.clear()  # 移除所有元素
print(A)  # set()

A = {1, 2, 3}
B = {3, 4, 5}
A.update(B)  # 添加元素
# A |= B  # 添加元素
print(A)  # {1, 2, 3, 4, 5}

A = {1, 2, 3}
B = {3, 4, 5}
A.difference_update(B)  # 移除元素
# A -= B  # 移除元素
print(A)  # {1, 2}

A = {1, 2, 3}
B = {3, 4, 5}
A.symmetric_difference_update(B)  # 移除相同元素
# A ^= B  # 移除相同元素
print(A)  # {1, 2, 4, 5}