二分查找 python实现

二分查找的python实现，经典的面试题，啥也不多说，直接上代码

def binary_search(num,list):
    low = 0
    high = len(list) - 1
    while(low <= high):
        middle = (low + high) / 2
        if list[middle] > num:
            high = middle - 1
        elif list[middle] < num:
            low = middle + 1
        else:
            return middle
    return -1

if __name__ == "__main__":
    list = [1,2,3,4,5,6,7,8,9]
    num = 4
    location = binary_search(num,list)
    print location