binary_search

def binary_search(searched_value, ordered_list):
    top_value = len(ordered_list)-1
    bottom_value = 0
    guess = (bottom_value+top_value)//2
    while top_value != bottom_value:
        if (searched_value < ordered_list[guess]):
            top_value = guess
        elif (searched_value > ordered_list[guess]):
            bottom_value = guess
        else:
            return True
        guess = (top_value + bottom_value) // 2
    return False