import random

alist = []
for i in range(1, 101):
    alist.append(i)
num = random.choice(alist)
# 请完善二分查找函数binary_search(),查找出num在列表alist里面的索引位置

def binary_search(alist,num):
    low = 0
    high = len(alist) - 1
    while True:
        mid = (low+high)//2
        guess = alist[mid]
        if guess == num:
            return mid
        elif guess < num:
            low = mid + 1
        else:
            high = mid - 1
    return None

result = binary_search(alist,num)
print(result)
print('找到的数字是',num,'，它在列表中的索引是',result)