Question

所以我希望Python使用csv读取器/写入器将目录中的所有CSV组合起来并合并它们，同时过滤掉包含第二列中任何其他行值的副本的任何行。

这是我的工作脚本：

import csv
import glob

with open('merged.csv','a') as out:
    seen = set()
    output = []
    out_writer = csv.writer(out)
    csv_files = [f for f in glob.glob('*.csv') if 'merged' not in f]
#csv_files = glob.glob('*.csv') 
     # I'd like to use all files including the output so that I don't
     # have to rename it when reusing the script - it should dupe-filter itself!
for filename in csv_files:
    with open(filename, 'rb') as ifile:
        read = csv.reader(ifile, delimiter=',')
        for row in read:
            if row[1] not in seen:
                seen.add(row[1])
                if row: #was getting extra rows
                    output.append(row)
out_writer.writerows(output)

我觉得我必须错过一些简单的事情。我的文件大小各约为100MB，我最终想要自动执行此操作，以便不同的计算机可以共享合并文件进行欺骗检查。

如需额外赠送金额，我如何更改此选项以检查同时包含row[1]和row[2]的行？（一旦dupe-filter和self-inclusion正在工作，当然......）

Answer 1

我建议使用pandas而不是csv writer。我会将你的代码重写为：

import pandas as pd
import glob

data = pd.concat([pd.DataFrame.from_csv(file) for
                  file in glob.glob("*.csv")]).drop_duplicates(cols=COLNAME_LIST)
data.to_csv('merged.csv')

在完全披露中我没有测试过这段代码，因为我没有大量的csv文件，但是我在成功之前写过类似的东西

Answer 2

这不仅仅是pandas可能需要的少量行，因为它是Python的库存，但另一方面它相对简单，将过滤多个列值，并处理重新读取以前的结果。它使用fileinput模块允许它将其多个输入文件视为单个连续的数据行流。

import csv
import fileinput
import glob
import os

merged_csv = 'merged.csv'
columns = (1, 2)  # columns used for filtering
pathname = '*.csv'
tmpext = os.extsep + "tmp"
csv_files = glob.glob(pathname)

if merged_csv not in csv_files:
    prev_merged = None
else:
    prev_merged = merged_csv + tmpext
    os.rename(merged_csv, prev_merged)
    csv_files[csv_files.index(merged_csv)] = prev_merged

with open(merged_csv, 'wb') as ofile:
    csv_writer = csv.writer(ofile)
    written = set()  # unique combinations of column values written
    csv_stream = fileinput.input(csv_files, mode='rb')
    for row in csv.reader(csv_stream, delimiter=','):
        combination = tuple(row[col] for col in columns)
        if combination not in written:
            csv_writer.writerow(row)
            written.add(combination)

if prev_merged:
    os.unlink(prev_merged)  # clean up

print '{!r} file {}written'.format(merged_csv, 're' if prev_merged else '')

使用特定于列的重复过滤器在Python中将行附加到CSV

2 个答案: