如何使用实际的 csv 文件而不是 stringIO 编写脚本答案

【问题标题】：How to write script using actual csv files rather than stringIO如何使用实际的 csv 文件而不是 stringIO 编写脚本
【发布时间】：2021-08-12 23:36:15
【问题描述】：

由于数据集太大，我如何编写以下脚本，该脚本使用导入的字符串 IO 将列标题重命名和重新排序为使用实际 csv 文件的格式。

from io import StringIO
from collections import OrderedDict
import csv

mystr = StringIO("""A;B;C;D
1;2;3;4
5;6;7;8""")

order = ['B', 'C', 'A', 'D']

# define renamed columns via dictionary
renamer = {'C': 'C2'}

# define column names after renaming
new_cols = [renamer.get(x, x) for x in order]

# replace mystr as open(r'file.csv', 'r')
with mystr as fin, open(r'C:\temp\out.csv', 'w', newline='') as fout:

# define reader / writer objects
reader = csv.DictReader(fin, delimiter=';')
writer = csv.writer(fout, delimiter=';')

# write new header
writer.writerow(new_cols)

# iterate reader and write row
for item in reader:
    writer.writerow([item[k] for k in order])

【问题讨论】：

标签： python csv rename import-csv

【解决方案1】：

您的代码的主要问题是with 代码需要缩进才能正常工作。以下是对您的代码的小改动，使其可以从一个 csv 读取并写入另一个：

from io import StringIO
from collections import OrderedDict
import csv

order = ['B', 'C', 'A', 'D']

# define renamed columns via dictionary
renamer = {'C': 'C2'}

# define column names after renaming
new_cols = [renamer.get(x, x) for x in order]

# replace mystr as open(r'file.csv', 'r')
with open('C:\tmp\in.csv') as fin, open(r'C:\temp\out.csv', 'w', newline='') as fout:
    # define reader / writer objects
    reader = csv.DictReader(fin, delimiter=';')
    writer = csv.writer(fout, delimiter=';')

    # write new header
    writer.writerow(new_cols)

    # iterate reader and write row
    for item in reader:
        writer.writerow([item[k] for k in order])

【讨论】：

这表明您的输入文件/数据没有“A”列。