如何用“||”替换第一个和最后一个“,”分隔符 来自 csv 而保留其他内容不变？

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

将每一行替换如下：

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

使用^([^,]*),|,(?=[^,]*$)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-aheadPython代码：import reregex = 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.

Answer 2

您可以拆分第一个（maxsplit=1从左起）和最后一个（maxsplit=1从右起）逗号并连接结果，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'