Difference between tuples that may have duplicates

Question

I have two tuples, which may or may not have duplicated elements. I want to remove elements of tuple a that also occur in tuple b, taking into account multiplicity. That is,

a = (1, 2, 3), b = (2, 3, 4) => (1)
a = (1, 2, 2, 3), b = (2, 3, 4) => (1, 2)
a = (1, 2, 3), b = (2, 2, 3, 4) => (1)

I want to use these tuples as keys for @lrucache, so I need a hashable type.

I'm not even sure how to do this by hand if there is no better way.

Edit: This is a Python question, which I realized might not be obvious.

Answer 1

You can subtract elements with their frequencies using Counter.

https://docs.python.org/3/library/collections.html#collections.Counter

from collections import Counter as c
a = (1, 2, 2, 3)
b = (2, 3, 4)



print(tuple((c(a)-c(b)).elements()))
(1,2)

---

Taking more complex example

from collections import Counter as c
a = (1, 2, 2, 2, 3, 5)
b = (2, 3, 4)



print(tuple((c(a)-c(b)).elements()))

#outputs

(1, 2, 2, 5)