如何使用Python合并CSV字符串中的字段？

Question

我尝试使用Python在CSV文件的每一行合并三个字段。这很简单，只是有些字段被双引号包围，并包含逗号。下面是一个例子：

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

有没有一个简单的算法可以用这种格式合并每行的字段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？

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模块来完成繁重的工作：http://docs.python.org/library/csv.html

你没有确切地说明你想如何合并列；大概你不想你的合并字段是“从波特兰，CTgoo移动”。下面的代码允许您指定分隔符字符串（可能是", "）并处理空/空字段。

[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中有一个用于解析CSV文件的内置模块：

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