如何用“||”替换第一个和最后一个“,”分隔符来自 csv 而其他人保持原样？

Question

我有一个 CSV 文件：

101, "Name1", "Designation1", "blah1", "Blah1", 20200914001
102, "Name2", "Designation2", "blah2", "Blah2", 20200914002
103, "Name3", "Designation3", "blah3", "Blah3", 20200914003
104, "Name4", "Designation4", "blah4", "Blah4", 20200914004
105, "Name5", "Designation5", "blah5", "Blah5", 20200914005

替换每一行，如下所示：

101|| "Name1", "Designation1", "blah1", "Blah1"|| 20200914001

类似的结构也适用于其余的行/记录。

我的代码替换了所有分隔符。

data = ""
with open('firstCSV.csv', 'r') as file:
    data = file.read().replace(',', '||').replace(' ', '')

with open("first_Out.csv", "w") as out_file:
    out_file.write(data)

提前致谢。

Answer 1

用

^([^,]*),|,(?=[^,]*$)

替换为\\1|| . 见证明。

解释

--------------------------------------------------------------------------------
  ^                        the beginning of the string
--------------------------------------------------------------------------------
  (                        group and capture to \1:
--------------------------------------------------------------------------------
    [^,]*                    any character except: ',' (0 or more
                             times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
  )                        end of \1
--------------------------------------------------------------------------------
  ,                        ','
--------------------------------------------------------------------------------
 |                        OR
--------------------------------------------------------------------------------
  ,                        ','
--------------------------------------------------------------------------------
  (?=                      look ahead to see if there is:
--------------------------------------------------------------------------------
    [^,]*                    any character except: ',' (0 or more
                             times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
    $                        before an optional \n, and the end of
                             the string
--------------------------------------------------------------------------------
  )                        end of look-ahead

蟒蛇代码：

import re

regex = r'^([^,]*),|,(?=[^,]*$)'
test_str = r'101, "Name1", "Designation1", "blah1", "Blah1", 20200914001'
subst = r'\1||'
print(re.sub(regex, subst, test_str))

结果： 101|| "Name1", "Designation1", "blah1", "Blah1"|| 20200914001 101|| "Name1", "Designation1", "blah1", "Blah1"|| 20200914001 101|| "Name1", "Designation1", "blah1", "Blah1"|| 20200914001 。

Answer 2

您可以拆分第一个（从左边开始maxsplit=1 ）和最后一个（从右边开始maxsplit=1 ）逗号并加入结果，例如：

>>> line = '101, "Name1", "Designation1", "blah1", "Blah1", 20200914001'

>>> first, rest = line.split(',', maxsplit=1)
>>> rest, last = rest.rsplit(',', maxsplit=1)
>>> '||'.join((first, rest, last))
'101|| "Name1", "Designation1", "blah1", "Blah1"|| 20200914001'