在哪里设置更新 CSV 文件的循环？

Posted 2023-02-15

【中文标题】在哪里设置更新 CSV 文件的循环？

【英文标题】：Where to set loop for updating CSV file?

【发布时间】：2022-01-15 13:19:48

【问题描述】：

Python 新手；任何有关格式、简单性、鼓舞人心的建议，不胜感激。

尝试编写一个脚本来搜索 CSV 中的 ID，更新同一 CSV 中该项目的记录，然后循环访问其他 ID。

如果我将“for this_item”循环放在“open with”命令中，嵌套的“for row”循环不会再次运行。我认为这是因为读取迭代已经被使用过一次。如果我在“打开方式”命令周围放置“for this_item”循环，我会得到：“ValueError: I/O operation on closed file”。

此外，这将用于多达 4,000 行和多达 30 列的 CSV - 我是否应该担心发生的重写量？

from datetime import  date
from tempfile import NamedTemporaryFile
import csv
import shutil

data = [['SKU', 'Color', 'Season', 'Angles', 'Delivered'], ['A1234', 'Red', 'Week 1', 'On-model, Pinup'], ['B4321', 'Black', 'Week 2', 'On-model'], ['JJ4567', 'Blue-Multi', 'Week 1', 'Pinup'], ['ClassicTee', 'Pink', 'Week 3', 'On-model, Pinup, Detail']]
fields = data[0]


# Write Demo CSV
with open('SKU_test.csv', 'w') as csv_file_write:
    csv_writer = csv.writer(csv_file_write, delimiter=',')
    for row in data:
        csv_writer.writerow(row)

test_csv = 'SKU_test.csv'

temp_file = NamedTemporaryFile(mode='w', delete=False)
today = date.today()

search_items = ['B4321', 'A1234']

for this_item in search_items:

    with open('SKU_test.csv', 'r') as csv_file, temp_file:
        reader = csv.DictReader(csv_file, fieldnames=fields)
        writer = csv.DictWriter(temp_file, fieldnames=fields)
        # reader_lists = list(reader)
        # print(reader_lists[1])

        for row in reader:
            print(row['SKU'])
            if row["SKU"] == str(this_item):
                print(f'Search match: row')
                row['Delivered'] = str(today)
            writer.writerow(row)
    shutil.move(temp_file.name, test_csv)
    
    

【问题讨论】：

您真的需要遍历搜索项吗？为什么不在单个循环中检查当前项目是否在 search_items 中？

if row["SKU"] in search_items:

【参考方案1】：

只需为所有搜索项处理一次文件，而不是循环搜索项。

search_items = 'B4321', 'A1234'

with open('SKU_test.csv', 'r') as csv_file, NamedTemporaryFile(mode='w', delete=False) as temp_file:
    reader = csv.DictReader(csv_file, fieldnames=fields)
    writer = csv.DictWriter(temp_file, fieldnames=fields)
    # reader_lists = list(reader)
    # print(reader_lists[1])

    for row in reader:
        print(row['SKU'])
        if row["SKU"] in search_items:
            print(f'Search match: row')
            row['Delivered'] = str(today)
        writer.writerow(row)
shutil.move(temp_file.name, test_csv)