truncate_amounts.py

def truncate_amounts_based_on_maximum(amounts, maximum):
    """Take from amounts until maximum is reached, possibly truncating the final amount.

    >>> truncate_amounts_based_on_maximum([10, 10], 15)
    [10, 5]
    >>> truncate_amounts_based_on_maximum([100], 0)
    []
    >>> truncate_amounts_based_on_maximum([1,1,1], 1)
    [1]
    """
    truncated = []

    for amount in amounts:
        maximum_reached = sum(truncated) >= maximum
        if maximum_reached:
            return truncated

        remaining_available = maximum - sum(truncated)
        truncated_amount = min(remaining_available, amount)
        truncated.append(truncated_amount)

    return truncated