regex - 用 Perl 标记逗号

Question

请解释这两行来自this code的Perl .

# separate out "," except if within numbers (5,300)
# previous "global" application skips some:  A,B,C,D,E > A , B,C , D,E
# first application uses up B so rule can't see B,C
# two-step version here may create extra spaces but these are removed later
# will also space digit,letter or letter,digit forms (redundant with next section)
$text =~ s/([^\p{IsN}])[,]/$1 , /g;
$text =~ s/[,]([^\p{IsN}])/ , $1/g;

Answer 1

您的代码进行了两次替换。 s/// 是一个替换，/g 标志告诉它全局，这本质上是替换所有.

这两行都使用了 \p{} unicode property character groups在正则表达式中。使用 IsN，它检查字符是否为数字。

/            
 (           # capture group
  [          # character group
   ^         # not the following characters
   \p{IsN}   # all characters that are a number
  ]
 )
 [,]         # followed by a comma
/

它用捕获的非数字、一个空格、一个逗号和一个空格替换它。

第二行做同样的事情，但逗号在前。

您可以重写此代码，使其更短、更简洁且具有相同的功能。 \P{} 是所有不具有此属性的字符，这消除了对 [] 的需要。这可以进一步缩短为 \PN。

$text =~ s/(\PN),/$1 , /g;
$text =~ s/,(\PN)/ , $1/g;