如何使用Python合并CSV字符串中的字段？

Question

我正在尝试使用Python在CSV文件的每一行中合并三个字段。这将很简单，除了一些字段被双引号括起来并包括逗号。下面是一个示例：

,,Joe,Smith,New Haven,CT,"Moved from Portland, CT",,goo,

有没有一种简单的算法可以为这种格式的每一行合并字段7-9？并非所有行都包含双引号中的逗号。

谢谢。

Answer 1

像这样的东西？

import csv
source= csv.reader( open("some file","rb") )
dest= csv.writer( open("another file","wb") )
for row in source:
    result= row[:6] + [ row[6]+row[7]+row[8] ] + row[9:]
    dest.writerow( result )

示例

>>> data=''',,Joe,Smith,New Haven,CT,"Moved from Portland, CT",,goo,
... '''.splitlines()
>>> rdr= csv.reader( data )
>>> row= rdr.next()
>>> row
['', '', 'Joe', 'Smith', 'New Haven', 'CT', 'Moved from Portland, CT', '', 'goo', '' ]
>>> row[:6] + [ row[6]+row[7]+row[8] ] +  row[9:]
['', '', 'Joe', 'Smith', 'New Haven', 'CT', 'Moved from Portland, CTgoo', '']

Answer 2

您可以使用csv模块来完成繁重的任务：http://docs.python.org/library/csv.html

您并没有确切地说明希望如何合并这些列；估计您不希望合并后的字段被“从Portland，CTgoo移来”。下面的代码允许您指定分隔符字符串(可能是", ")并处理空/空白字段。

[transcript of session]
prompt>type merge.py
import csv

def merge_csv_cols(infile, outfile, startcol, numcols, sep=", "):
    reader = csv.reader(open(infile, "rb"))
    writer = csv.writer(open(outfile, "wb"))
    endcol = startcol + numcols
    for row in reader:
        merged = sep.join(x for x in row[startcol:endcol] if x.strip())
        row[startcol:endcol] = [merged]
        writer.writerow(row)

if __name__ == "__main__":
    import sys
    args = sys.argv[1:6]
    args[2:4] = map(int, args[2:4])
    merge_csv_cols(*args)

prompt>type input.csv
1,2,3,4,5,6,7,8,9,a,b,c
1,2,3,4,5,6,,,,a,b,c
1,2,3,4,5,6,7,8,,a,b,c
1,2,3,4,5,6,7,,9,a,b,c

prompt>\python26\python merge.py input.csv output.csv 6 3 ", "

prompt>type output.csv
1,2,3,4,5,6,"7, 8, 9",a,b,c
1,2,3,4,5,6,,a,b,c
1,2,3,4,5,6,"7, 8",a,b,c
1,2,3,4,5,6,"7, 9",a,b,c

Answer 3

Python中有一个内置模块，用于解析CSV文件：

http://docs.python.org/library/csv.html