解决TypeError：int()参数不能为list类型的Python代码修正问题

问题背景 #

需要实现功能：传入文件名和列名列表，返回所有行中这些列的整数值组成的列表（整数顺序无关）。当前代码中指定行触发错误：

def extract_data(filename, column_names):
    with open(filename) as election:
        elects = [row for row in csv.DictReader(election)]
    results = ([row[cn].replace(",", "")
                for cn in column_names] for row in elects)
    results = [row for row in results if '' not in row]
    return list((results))


def extract_election_votes(filename, column_names):
    results = extract_data(filename, column_names)
    # 以下行触发错误
    return [int(vote) for vote in results] 

报错信息：

TypeError: int() argument must be a string, a bytes-like object or a number, not 'list'

问题分析 #

extract_data函数返回的是二维列表：外层列表的每个元素对应一行数据，是包含多个列字符串值的子列表。原代码直接遍历外层列表，把每个子列表（而非子列表里的字符串）传给int()，导致类型不匹配错误。

解决方案 #

根据需求（返回所有行中这些列的整数值组成的一维列表，顺序无关），需要嵌套遍历二维列表的每个元素，将其转为整数后合并，修改触发错误的行如下：

return [int(vote) for row in results for vote in row]

如果需要保留每行的结构（返回二维整数列表，每个子列表对应一行的列整数），则修改为：

return [[int(vote) for vote in row] for row in results]

完整修正代码 #

注意：原代码缺少csv模块导入，需要补上：

import csv

def extract_data(filename, column_names):
    with open(filename) as election:
        elects = [row for row in csv.DictReader(election)]
    results = ([row[cn].replace(",", "")
                for cn in column_names] for row in elects)
    results = [row for row in results if '' not in row]
    return results  # 简化list(results)，因为results已经是列表类型

def extract_election_votes(filename, column_names):
    results = extract_data(filename, column_names)
    return [int(vote) for row in results for vote in row]

内容的提问来源于stack exchange，提问作者user19563024