def knapsack(items, capacity):
    if type(capacity) is not int or capacity < 0:
        raise ValueError("Nonnegative integer capacity required")
    if any(not isinstance(name, str) or type(weight) is not int or weight <= 0 or type(value) is not int or value < 0 for name, weight, value in items):
        raise ValueError("Invalid named item")
    if len({name for name, _, _ in items}) != len(items):
        raise ValueError("Unique item names required")
    if (len(items) + 1) * (capacity + 1) > 100000:
        raise ValueError("Teaching table budget exceeded")
    table = [[0] * (capacity + 1) for _ in range(len(items) + 1)]
    for row, (_, weight, value) in enumerate(items, 1):
        for room in range(capacity + 1):
            table[row][room] = table[row - 1][room]
            if weight <= room:
                table[row][room] = max(table[row][room], value + table[row - 1][room - weight])
    chosen, room = [], capacity
    for row in range(len(items), 0, -1):
        if table[row][room] != table[row - 1][room]:
            name, weight, _ = items[row - 1]
            chosen.append(name)
            room -= weight
    return table[-1][capacity], list(reversed(chosen))

items = [("net", 3, 7), ("crate", 2, 4), ("tag", 1, 2)]
value, chosen = knapsack(items, 4)
records = {name: (weight, score) for name, weight, score in items}
weight = sum(records[name][0] for name in chosen)
score = sum(records[name][1] for name in chosen)
assert len(chosen) == len(set(chosen)) and weight <= 4 and score == value
print(chosen)
print(weight, score)