import random

alist = [1,2,3,4,5,6,7,8,9]
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):
    a=0
    j=len(alist)-1
    while a<=j:
        g=(a+j)//2
        f=alist[g]
        if f==9:
            print('找到了')
            break
        elif f<9:
            a=g+1
        else:
            j=g-1
    return None
r=binary_search(alist,9)