在 CSV 文件中追加数据时列表索引超出范围

Question

我有一个 CSV 文件，其中有三列数据，我想在检查数据存在后添加新行，然后想在新行中添加这些数据，但出现错误 list index out of range

这是我的代码

类别

name
apple
banana
potatoes
onion

CSV 数据

titles,summaries,terms
apple,,Apple (Fruit)
banana,,Banana (Fruit)
potatoes,,Potato (Vegitable)
onion,,Onion (Vegitable)

categories = db.table('categories').get()

csv_data = csv.reader(open('categories.csv', "r"))

csv_matched_strings = []
for row in csv_data:
    for category in categories:
        if category.name in row[0]:
            print(row[0] + ': ' + row[2])
            csv_matched_strings.append(category.name)
            List = [row[0],'',row[2]]
            with open('categories.csv', 'a+') as f_object:
                writer_object = writer(f_object)
                writer_object.writerow(List)
                f_object.close()

注意：数据添加到现有的 CSV 文件中，但 CSV 文件在每个循环之间写入一个空行。

Answer 1

原始解决方案的主要问题是处理文件。外部 for 循环不会停止，因为内部 for 循环正在将行附加到工作文件。

在这里，我使用了一个简单的列表来存储需要复制的内容。如果文件太大，另一种选择是使用第二个 CSV 文件 作为缓冲区，然后在最后将其复制回来。

此外，考虑使用 sets when doing look-ups and maybe learn about how the in operator works here is a post you might find helpful。

import csv
from csv import writer

# Since OP hasn't provided the class, consider this a substitute
categories = [
    {'name': 'apple'},
    {'name': 'banana'},
    {'name': 'potatoes'},
    {'name': 'onion'},
]

# set of category names created using a set comprehension
cat = {c['name'] for c in categories}

found_rows = []
csv_matched_strings = []

with open('categories.csv', "r") as f:
    csv_data = csv.reader(f)

    for row in csv_data:
        if row[0] in cat:
            # First value is found in categories
            print(row[0] + ': ' + row[2])
            found_rows.append([row[0], '', row[2]])
            # I left it here since it was there in the original code
            csv_matched_strings.append(row[0])

# categories.csv is now closed.
# We open it again in append mode and proceed to append the duplicates
with open('categories.csv', 'a+') as f:
    writer_object = writer(f)
    for row in found_rows:
        writer_object.writerow(row)

在 CSV 文件中追加数据时列表索引超出范围

list index out of range when appending data in CSV file

python

csv