关于TypeError: list indices must be integers or slices, not float报错

def binary_search(list,item):
    low = 0
    high = len(list) - 1
    while low <= high:
        mid=(low+high)/2
        guess=list[mid]
        if guess == item:
            return mid
        if guess > item:
            high = mid - 1
        else:
            low = mid + 1
    return None
my_list=[1,3,5,7,9]
print(binary_search(my_list,3))

经查阅得到“/”是浮点数除法，但是在此程序中需要整除，所以要用“%”或者“//”

def binary_search(list,item):
    low = 0
    high = len(list) - 1
    while low <= high:
        mid=(low+high)%2#这里报错错了，
        guess=list[mid]
        if guess == item:
            return mid
        if guess > item:
            high = mid - 1
        else:
            low = mid + 1
    return None
my_list=[1,3,5,7,9]
print(binary_search(my_list,3))