chopmax.py

#!/usr/bin/env python3

def chopmax(seq, size):
    rest = {}
    for item, amount in seq:
        while amount:
            # print("item:", item, "- amount:", amount)
            if not rest and amount >= size:
                amount -= size
                # print("chunk:", {item: size})
                yield item  # uniform chunk
            else:
                missing = size - sum(rest.values())
                added = min(amount, missing)
                rest[item] = rest.get(item, 0) + added
                amount -= added
                if added == missing:
                    # print("chunk:", rest)
                    yield max(rest.items(), key=lambda kv: kv[1])[0]
                    rest = {}
    if rest:
        # print("chunk:", rest)
        yield max(rest.items(), key=lambda kv: kv[1])[0]

if __name__ == "__main__":
    inp=[("a",2), ("b",7), ("c",3)]
    print(inp, list(chopmax(inp, 5)))
    inp=[("a", 21), ("b", 1), ("c", 5), ("d", 12)]
    print(inp, list(chopmax(inp, 5)))