将一行数据附加到大型 CSV 文件中的第 2 行

Question

我确信这是一个非常简单的问题，但我似乎找不到任何相关信息。我有一个非常大的 CSV 文件，我需要在标题后面直接插入一行，这有助于读取 csv 并将其连接到地块 shapefile 的另一个代码。我有代码来附加我想要的数据行，但它只会转到最后一行。我无法弄清楚如何让代码在标题行之后立即插入我的行。这是我的代码：import osimport csvinsert_row = '"AAAAAAAAAAAAAAAAAAA","**********","**********","**********","**********","**********","**********","**","**********","**********","****","**********",999999,9999,00'os.chdir(r"D:\PROPERTY\PINELLAS\Data_20201001_t")with open("owner_mail.csv", 'r') as csv_file, open("owner_mail.csv", 'a', newline = "") as new_file:    csv_reader = csv.reader(csv_file)    csv_writer = csv.writer(new_file)    csv_writer.writerow(insert_row)就是这样了。我只需要 insert_row 行数据位于第 2 行位置，而不是位于文件末尾。谢谢。

Answer 1

除非替换完全相同长度的数据，否则不能只在文件中间插入一行。您必须读取整个文件，对其进行编辑，然后重新写入。

像这样的东西应该有效：

import csv

# This must be an iterable not a string

insert_row = "AAAAAAAAAAAAAAAAAAA","**********","**********","**********","**********","**********","**********","**","**********","**********","****","**********",999999,9999,00

with open("owner_mail.csv", 'r') as csv_file, open("owner_mail_updated.csv", 'w', newline = "") as new_file:

    csv_reader = csv.reader(csv_file)

    csv_writer = csv.writer(new_file)

    header = next(csv_reader)

    csv_writer.writerow(header)

    csv_writer.writerow(insert_row)

    for line in csv_reader:

        csv_writer.writerow(line)

如果 CSV 文件不太大而无法完全放入内存，那么您可以一次读取所有行，对其进行编辑，然后将它们写回到同一个文件中。一旦出现问题，风险就更大。更安全地写入新文件，然后删除原始文件并重命名（如果没有错误）：

import csv

# This must be an iterable not a string

insert_row = "AAAAAAAAAAAAAAAAAAA","**********","**********","**********","**********","**********","**********","**","**********","**********","****","**********",999999,9999,00

with open("owner_mail.csv", 'r') as csv_file:

    rows = list(csv.reader(csv_file))

rows.insert(1,insert_row)  # insert after header row

with open("owner_mail.csv", 'w') as csv_file:

    w = csv.writer(csv_file)

    w.writerows(rows)

Answer 2

请尝试这个：

import os

import csv

insert_row = '"AAAAAAAAAAAAAAAAAA","**********","**********","**********","**********","**********","**********","**","**********","**********","****","**********",999999,9999,00'

with open("owner_mail.csv", 'r') as csv_file, open("owner_mail.csv", 'w') as new_file:

  csv_reader = csv.reader(csv_file)

  reader = list(csv_reader)

  reader.insert(1,insert_row)

  csv_writer = csv.writer(new_file)

  csv_writer.writerows(reader)