python实现二分查找

学到递归算法来记录一下二分查找的递归算法的实现：

def search(sequence, number, lower, upper):
    if upper is None:
        upper = len(sequence) - 1
    if lower == upper:
        assert number == sequence[upper]
        return upper

    else:
        middle = (lower + upper) // 2
        if number > sequence[middle]:
            return search(sequence, number, middle + 1, upper)
        else:
            return search(sequence, number, lower, middle)