Python讀取CSV文件，並寫入其他跳過列

Question

我有18列的CSV輸入文件，我需要使用輸入的所有列（第4列和第5列除外）創建新的CSV文件

我的功能現在看起來像

def modify_csv_report(input_csv, output_csv):
    begin = 0
    end = 3

    with open(input_csv, "r") as file_in:
        with open(output_csv, "w") as file_out:
            writer = csv.writer(file_out)
            for row in csv.reader(file_in):
                writer.writerow(row[begin:end])
    return output_csv

所以它讀取和寫入第0-3列，但是我不知道如何跳過第4,5列並從那里繼續

Answer 1

您可以使用slicing添加行的另一部分，就像對第一部分所做的那樣：

writer.writerow(row[:4] + row[6:])

請注意，要包括第3列，第一個切片的停止索引應為4。通常也不必指定開始索引0。

更通用的方法是使用列表理解並enumerate ：

exclude = (4, 5)
writer.writerow([r for i, r in enumerate(row) if i not in exclude])

Answer 2

如果您的CSV具有有意義的標頭，則可以使用DictReader和DictWriter類來按索引對行進行切片。

#!/usr/bin/env python
from csv import DictReader, DictWriter

data = '''A,B,C
1,2,3
4,5,6
6,7,8'''

reader = DictReader(data.split('\n'))

# You'll need your fieldnames first in a list to ensure order
fieldnames = ['A', 'C']
# We'll also use a set for efficient lookup
fieldnames_set = set(fieldnames)

with open('outfile.csv', 'w') as outfile:
    writer = DictWriter(outfile, fieldnames)
    writer.writeheader()
    for row in reader:
        # Use a dictionary comprehension to iterate over the key, value pairs
        # discarding those pairs whose key is not in the set
        filtered_row = dict(
            (k, v) for k, v in row.iteritems() if k in fieldnames_set
        )
        writer.writerow(filtered_row)

Answer 3

這就是你想要的：

import csv


def remove_csv_columns(input_csv, output_csv, exclude_column_indices):
    with open(input_csv) as file_in, open(output_csv, 'w') as file_out:
        reader = csv.reader(file_in)
        writer = csv.writer(file_out)
        writer.writerows(
            [col for idx, col in enumerate(row)
             if idx not in exclude_column_indices]
            for row in reader)

remove_csv_columns('in.csv', 'out.csv', (3, 4))