二分找 24 要几步

在排好序的 [13, 15, 17, 23, 24] 里二分查找 24。运行下面这段程序，它数的是"比了几次"：

def bsearch_steps(a, target):
    lo = 0
    hi = len(a) - 1
    steps = 0
    while lo <= hi:
        mid = (lo + hi) // 2
        steps += 1
        if a[mid] == target:
            return steps
        if a[mid] < target:
            lo = mid + 1
        else:
            hi = mid - 1
    return steps

print(bsearch_steps([13, 15, 17, 23, 24], 24))