如何使用python选择CSV文件中的第N行 [英] How to select every Nth row in CSV file using python

问题描述

我有一个包含数百行的CSV文件，我想选择每3行并将其导出到一个新的CSV文件中，并将新的输出CSV文件命名为所选内容的第一行.

I have a CSV file with hundreds of rows, and I would like to select and export every 3 rows to a new CSV file with the new output CSV file being named after the first row of the selection.

例如在以下CSV文件中....

For example in the following CSV file....

1980 10 12            
1  2  3  4  5  6  7       
4  6  8  1  0  8  6  
1981 10 12
2  4  9  7  5  4  1  
8  9  3  8  3  7  3

我想选择前3行，并根据第一行导出到名为"1980 10 12"的新CSV，然后选择后3行，并根据以下内容导出到名为"1981 10 12"的新CSV接下来的3行中的第一行.我想使用python做到这一点.

I would like to select the first 3 rows and export to a new CSV named "1980 10 12" based on the first row then select the next 3 rows and export to a new CSV named "1981 10 12" based on the first row of the next 3 rows. I would like to do this using python.

推荐答案

使用 csv 模块，以及 itertools.islice() 每次选择3行:

Using the csv module, plus itertools.islice() to select 3 rows each time:

import csv
import os.path
from itertools import islice


with open(inputfilename, 'rb') as infh:
    reader = csv.reader(infh)
    for row in reader:
        filename = row[0].replace(' ', '_') + '.csv')
        filename = os.path.join(directory, filename)
        with open(filename, 'wb') as outfh:
            writer = csv.writer(outfh)
            writer.writerow(row)
            writer.writerows(islice(reader, 2))

writer.writerows(islice(reader，2))行从读取器中获取接下来的两行，并在写入当前行(带有日期)后将它们复制到写入器CSV中首先到输出文件.

The writer.writerows(islice(reader, 2)) line takes the next 2 rows from the reader, copying them across to the writer CSV, after writing the current row (with the date) to the output file first.

您可能需要调整 csv.reader()和 csv.writer()对象的定界符参数；默认值为逗号，但是您没有指定确切的格式，也许您需要将其设置为'\ t'标签.

You may need to adjust the delimiter argument for the csv.reader() and csv.writer() objects; the default is a comma, but you didn't specify the exact format and perhaps you need to set it to a '\t' tab instead.

如果使用的是Python 3，请使用'r'和'w'文本模式打开文件，并设置 newline =''两者皆有； open(inputfilename，'r'，newline ='')和 open(filename，'w'，newline ='').

If you are using Python 3, open the files with 'r' and 'w' text mode, and set newline='' for both; open(inputfilename, 'r', newline='') and open(filename, 'w', newline='').

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