norvig

from collections import Counter, namedtuple

def is_prime(i) -> bool: return all(i % p for p in range(2, i))

def primes(N): return [p for p in range(2, N) if is_prime(p)]

# Set: `ints` are a set of integers that total to `sum`;
# `need` is a Counter of digits that are needed to complete the Set.
Set = namedtuple('Set', 'ints, sum, need')