【Python】数据结构：集合，花括号表示{}

1.集合

Python中的集合与数学上的集合是一致的，不允许有重复元素，而且可以进行交集、并集、差集等运算。

2.创建集合

#字面量方式
set1 = {1, 2, 3, 3, 3, 2}
print(set1)  # {1, 2, 3}
print('length = ', len(set1))  # length =  3

#构造器语法
set2 = set(range(1, 10))
set3 = set((1, 2, 3, 3, 2, 1))
print(set2, set3)  # {1, 2, 3, 4, 5, 6, 7, 8, 9} {1, 2, 3}

#推导式语法
set4 = {num for num in range(1, 100) if num % 3 == 0 or num % 5 == 0}   # {3, 5, 6, 9, 10, 12, 15, 18...
print(set4)

3.集合添加和删除元素

set1.add(4)  # 添加
set1.add(5)
print(set1)  # {1, 2, 3, 4, 5}

set2.update([11, 12])
print(set2)  # {1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12}

set2.discard(5)  # 移除5
print(set2)  # {1, 2, 3, 4, 6, 7, 8, 9, 11, 12}

if 4 in set2:
    set2.remove(4)  # 移除4
print(set2)  # {1, 2, 3, 6, 7, 8, 9, 11, 12}

print(set3.pop())  # 1
print(set3)  # {2, 3}

4.集合运算

print(set1 & set2)  # {1, 2, 3} 交集
print(set1.intersection(set2))

print(set1 | set2)  # {1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12} 并集
print(set1.union(set2))

print(set1 - set2)  # {4, 5} 差集
print(set1.difference(set2))

print(set1 ^ set2)  # {4, 5, 6, 7, 8, 9, 11, 12}
print(set1.symmetric_difference(set2))

5.判断子集和超集

print(set2 <= set1)  # False
print(set2.issubset(set1))

print(set3 <= set1)  # True
print(set3.issubset(set1))

print(set1 >= set2)  # False
print(set1.issuperset(set2))

print(set1 >= set3)  # True
print(set1.issuperset(set3))

参考链接
1.集合中删除元素的区别remove()-discard()-pop()-clear()