Question

我必须在python中将几个列表作为列添加到现有CSV文件中。我想为输出CSV使用一个临时文件，因为我想对该结果数据的前两列进行排序，然后写入新的最终CSV文件。我不想保留未排序的csv文件，这就是为什么我要在该步骤中使用tempfile.NamedTemporaryFile的原因。最终CSV文件中没有任何内容，但没有其他代码错误。我更改了 with 块的缩进方式，但无法修复。我通过使用磁盘上的文件进行了测试，效果很好。我需要帮助来了解我在做什么错。这是我的代码：


# Open the existing csv in read mode and new temporary csv in write mode
with open(csvfile.name, 'r') as read_f, \
    tempfile.NamedTemporaryFile(suffix='.csv', prefix=('inter'), mode='w', delete=False) as write_f:
    csv_reader = csv.reader(read_f)
    csv_writer = csv.writer(write_f)
    i = 0
    for row in csv_reader:
        # Append the new list values to that row/list 
        row.append(company_list[i])
        row.append(highest_percentage[i])
        # Add the updated row / list to the output file
        csv_writer.writerow(row)
        i += 1

    with open(write_f.name) as data:
        stuff = csv.reader(data)  
        sortedlist = sorted(stuff, key=operator.itemgetter(0, 1))
    #now write the sorted result into final CSV file
    with open(fileout, 'w', newline='') as f:
        fileWriter = csv.writer(f)
        for row in sortedlist:
            fileWriter.writerow(row)

Answer 1

您应该插入一个write_f.seek(0, 0)

在打开临时文件的行之前：

    write_f.seek(0, 0)
    with open(write_f.name) as data:

Answer 2

我发现了导致IndexError的原因，并因此导致了空的最终CSV。我借助CSV file written with Python has blank lines between each row解决了这个问题。这是我更改后的代码，可以正常运行：

with open(csvfile.name, 'r') as read_f, \
    tempfile.NamedTemporaryFile(suffix='.csv', prefix=('inter'), newline='', mode='w+', delete=False) as write_f:
    csv_reader = csv.reader(read_f)
    csv_writer = csv.writer(write_f)
    i = 0
    for row in csv_reader:
        # Append the new list values to that row/list 
        row.append(company_list[i])
        row.append(highest_percentage[i])
        # Add the updated row / list to the output file
        csv_writer.writerow(row)
        i += 1

with open(write_f.name) as read_stuff, \
    open(fileout, 'w', newline='') as write_stuff:
    read_data = csv.reader(read_stuff)
    write_data = csv.writer(write_stuff)
    sortedlist = sorted(read_data, key=operator.itemgetter(0, 1))
    for row in sortedlist:
        write_data.writerow(row)

写入Python中的临时csv文件以读取该文件进行排序，然后写入另一个文件会产生空结果

2 个答案: