正则表达式前导空格/在标点符号之前/添加尾随空格

Question

为了更好地清理我的论坛消息语料库，我想使用两个正则表达式删除标点符号之前的前导空格，并在需要时添加一个标点符号之后的空格。后者没有问题( (?<=[.,!?()])(?! ) )，但我至少对第一个有一些问题。

我使用了这个表达式:\s([?.!,;:"](?:\s|$))

但到目前为止还不够灵活:

• 即使标点符号前面已经有一个空格(或更多)，它也会匹配
• 如果标点符号后面没有空格则不匹配
• 它与任何未列出的标点符号都不匹配(但我想我最终可以使用 [:punct:] 来实现这一点)

最后，两者都匹配小数点(虽然不应该)

我最终如何重写表达式来满足我的需求？

示例字符串和预期输出

This is the end .Hello world! # This is the end. Hello world! (remove the leading, add the trailing)
This is the end, Hello world! # This is the end, Hello world! (ok!)
This is the end . Hello world! # This is the end. Hello world! (remove the leading, ok the trailing)
This is a .15mm tube # This is a .15 mm tube (ok since it's a decimal point)

Answer 1

使用\p{P}匹配所有标点符号。使用\h*而不是\s*因为\s也会匹配换行符。

(?<!\d)\h*(\p{P}+)\h*(?!\d)

将匹配的字符串替换为 \1<space>

DEMO

> x <- c('This is the end .Stuff', 'This is the end, Stuff', 'This is the end . Stuff', 'This is a .15mm tube')
> gsub("(?<!\\d)\\h*(\\p{P}+)\\h*(?!\\d)", "\\1 ", x, perl=T)
[1] "This is the end. Stuff" "This is the end, Stuff" "This is the end. Stuff"
[4] "This is a .15mm tube"