交集、并集、差集

交集合
cat=['fish','beef','pig']
dog=['beef','pig']
#列表转变为集合
cat1=set(cat)
dog1=set(dog)
print(cat1,dog1)               输出{'pig', 'beef', 'fish'} {'pig', 'beef'}
print(cat1.intersection(dog1)) 输出{'pig', 'beef'}
print(cat1&dog1)               输出{'pig', 'beef'}

并集
cat=['fish','beef','pig']
dog=['beef','pig']
#列表转变为集合
cat1=set(cat)
dog1=set(dog)
print(cat1.union(dog1)) 输出 {'fish', 'pig', 'beef'}
print(cat1|dog1)        输出{'fish', 'pig', 'beef'}

差集
cat=['fish','beef','pig']
dog=['beef','pig']
#列表转变为集合
cat1=set(cat)
dog1=set(dog)
print(cat1-dog1)
print(cat1.difference(dog1))