Question

我试图在这个python程序中读取一个csv文件作为列表。 test.csv文件只包含一行不同的数字。我想找到总和等于500的数字的可能组合，并在以列表形式输出后，python程序会将此列表附加到我的test.csv文件中。

csv_file.py

import sys
import csv
import os

file_name="test.csv"
path1 = "C:\MAYANK\python p"
path2 = os.path.join(path1, file_name)

with open(path2, 'r') as csv_file:
   reader = csv.reader(csv_file, delimiter=",")
   row1 = list(reader)


def subset_sum(numbers, target, partial=list()):
    s = sum(partial)
    # check if the partial sum is equals to target
    if s == target:
        with open(path2, 'a') as csv_file1:
        writer = csv.writer(csv_file1)
        writer.writerow(partial)

    if s >= target:
        return  # if we reach the number why bother to continue

    for i in range(len(numbers)):
        n = numbers[i]
        remaining = numbers[i + 1:]
        subset_sum(remaining, target, partial + [n])

if __name__ == '__main__':
    subset_sum(row1, 500)

我已编写所有代码但收到此错误：

Traceback (most recent call last):
File "csv_file.py", line 33, in <module>
 subset_sum(row1, 500)
File "csv_file.py", line 30, in subset_sum
 subset_sum(remaining, target, partial + [n])
File "csv_file.py", line 17, in subset_sum
  s = sum(partial)
TypeError: unsupported operand type(s) for +: 'int' and 'list'

Answer 1

with open(path2, 'r') as csv_file:
   reader = csv.reader(csv_file, delimiter=",")
   row1 = list(reader)

您的输入/您如何导入它是您的问题：

>>> subset_sum([111,222,333,444,555, 499, 1, 389, 20, 369], 500)
[111, 389]
[111, 20, 369]
[499, 1]

有效，同时：

>>> subset_sum([111,222,333,444,555, [499], 1, 389, 20, 369], 500)
TypeError: unsupported operand type(s) for +: 'int' and 'list'

没有。

reader必须是嵌套列表，然后sum([[]])会TypeError: unsupported operand type(s) for +: 'int' and 'list'

修复输入后

，您可能会获得

TypeError: unsupported operand type(s) for +: 'int' and 'str'

这意味着您需要将该列表映射到整数。要解决此问题，请将list()调用替换为map(int, )：

with open(path2, 'r') as csv_file:
   reader = csv.reader(csv_file, delimiter=",")
   row1 = map(int, reader)

Answer 2

list(reader)为您提供行列表，其中每行都是字符串列表。换句话说，您的row1是列表，而不是数字列表，这就是sum()抛出该特定异常的原因。

您将其命名为row1这一事实表明您只对第一行感兴趣。如果是这样，那么您实际上是想说row1 = list(reader)[0]，这将为您提供sum()可以处理的列表。但要注意，如果你这样做，你将失去对表格其余部分的访问权。

第二个问题是你需要将单个条目从字符串转换为数字，否则你不会得到你可能期望从sum()获得的结果。

要在将整个表格从字符串转换为数字时保留整个表格，您可以这样做：

with open(path2, 'r') as csv_file:
    reader = csv.reader(csv_file, delimiter=",")
    table = [[float(x) for x in row] for row in reader]
    row1 = table[0]

然后像以前一样继续。

+：＆＃39; int＆＃39;不支持的操作数类型和＆＃39;列出＆＃39;

2 个答案: