设置与返回每个匹配项的交集

Question

everyone!

I'm looking for most elegant way to find intersection of two sets, but I need to get a every match of keys

The examples of what I mean:

s1 = {1, 1, 2, 3}
s2 = {4, 5, 1, 1}
s1.intersection(s2)

Output is:

{1}

What output I need:

{1, 1}

Thank you everyone for help and sorry for my english

Answer 1

If you want a set-like thing for which items can appear with multiplicity greater than 1, then you could use a multiset . These can be represented by Counter objects. There is no built-in intersection method for those, but you could write a function which computes it by taking the min of two counts:

from collections import Counter

def intersection(s1,s2):
    '''intersection of multisets s1,s2'''
    d = {}
    for i in s1:
        c = min(s1[i],s2[i])
        if c > 0:
            d[i] = c
    return Counter(d)

#test:

s1 = Counter([1, 1, 2, 3])
s2 = Counter([4, 5, 1, 1])

print(s1)
print(s2)
print(intersection(s1,s2))

Output:

Counter({1: 2, 2: 1, 3: 1})
Counter({1: 2, 4: 1, 5: 1})
Counter({1: 2})