python - 如果 CSV 行存在于随机样本中，则更新该行

Question

得到一个 CSV，我使用以下代码选择 500 行的随机样本:

import csv
import random

with open('Original.csv' , "rb") as source:
    lines = [line for line in source]

random_choice = random.sample(lines, 500);

我想做的是更新名为 [winner] 的列(如果它们存在于示例中)，然后将其保存回 csv 文件，但我不知道如何实现此目的...

名为 [ID] 的列中有一个唯一标识符。

我该如何去做呢？

Answer 1

从如下所示的 CSV 开始:

ID  something   winner
1   a   
2   b   
3   c   
4   a   
5   d   
6   a   
7   b   
8   e   
9   f   
10  g

您可以使用以下方法。读入整个文件，通过随机选择的索引选择行，然后写回文件。

import csv
import random

# Read in the data
with open('example.csv', 'r') as infile:
    reader = csv.reader(infile)
    header = next(reader) # We want the headers, but not as part of the sample
    data = []
    for row in reader:
        data.append(row)

# Find the column called winner
winner_column_index = header.index('winner')

# Pick some random indices which will be used to generate the sample
all_indices = list(range(len(data)))

sampled_indices = random.sample(all_indices, 5)

# Add the winner column to those rows selected
for index in sampled_indices:
    data[index][winner_column_index] = 'Winner'

# Write the data back
with open('example_out.csv', 'w', newline='') as outfile:
    writer = csv.writer(outfile)
    writer.writerow(header) # Make sure we get the headers back in
    writer.writerows(data) # Write the rest of the data

这将给出以下输出:

ID  something   winner
1   a   
2   b           Winner
3   c   
4   a           Winner
5   d   
6   a           Winner
7   b   
8   e   
9   f           Winner
10  g           Winner

编辑:事实证明，如果您想使用 Excel 打开，将 CSV 的第一列称为 ID 并不是一个好主意。然后它错误地认为该文件是 SYLK 格式。