Python异常: TypeError: 'list' object is not callable

错误代码

报错的代码片段

def merge_sort(items, comp=lambda x, y: x < y):
    items_len = len(items)

    if items_len < 2:
        return items[:]

    mid = items_len // 2
    left = merge_sort(items[:mid], comp)
    right = merge_sort(items[mid:], comp)

    return merge(left, right, comp)


def merge(first, second, comp):
    result = []

    left_index = 0
    right_index = 0

    while left_index < len(first) and right_index < len(second):
        if comp(first[left_index], second(right_index)):
            result.append(first[left_index])
            left_index += 1
        else:
            result.append(second[right_index])
            right_index += 1
    result += first[left_index:]
    result += second[right_index:]

    return result

错误原因

second参数传入的是一个列表(list), second(right_index)这是一个函数的调用方式, 而列表是不能被调用的，因此抛出一个类型错误.