数据结构与算法（查找）

def linear_search(data_list, value):
    for index, i in enumerate(data_list):
        if i == value:
            return index
    else:
        return None

def binary_search(data_list, value):
    left = 0
    right = len(data_list)
    while left <= right:
        mid = (left + right) // 2
        if mid == value:
            return mid
        elif mid < value:
            left = mid + 1
        else:
            right = mid -1
    else:
        return None