sum pairs for num

''' finds all possible pairs of integers within defined range that will add up to a target number
and returns those as a list of tuples. One or more digits can be excluded from the solutions by
passing one or more integers (int, tuple or int, list of int, None) '''

def excludes_digits(num, digits=None):
    if not digits:
        return True
    if isinstance(digits, int):
        digits = [digits]
    num_str = str(num)
    for digit in digits:
        if str(digit) in num_str:
            return False
    return True

def find_sums(arr, target, excluded=None):
    finds = set()
    hash = set()
    if target % 2 == 0:  # if target is even need to allow for half + half in arr
        even = target // 2
        if arr.count(even) > 1:
            source = list(set(arr)) + [even]  # half in arr twice, need unique numbers but 2 off half
        else:
            source = set(arr)  # half not in arr twice so make sure we have unique numbers
    else:
        source = set(arr)  # half not in arr so make sure we have unique numbers
    for num in source:
        if excludes_digits(num, excluded):
            candidate = target - num
            if excludes_digits(candidate, excluded) and candidate in hash:
                finds.add((num, candidate))
            hash.add(num)
    return finds

# example usage
target = 24  # number to find sums for, i.e. pairs of numbers that add up to target
exclude = 9, 4  # one or more single digit integers that should be excluded from solutions

# need to provide a container (list, tuple, set) of numbers that can be used for solutions
# generated here using a linear range and adding in additional copy of half of target
# if target is an even number
lowest = -6 #
highest = 32 # or maybe use target - lowest
candidates = list(range(lowest, highest + 1)) + ([target // 2] if target % 2 == 0 else [])

# look for solutions using numbers referenced by candidates
finds = find_sums(candidates, target, exclude)
print(sorted(finds))