R语言：多字符分隔符分割字符串并保留分隔符的实现需求

需求说明 #

• 条目拆分：长字符串中的每个条目以**可变长度数字+制表符(\t)**开头，拆分时需保留该条目编号前缀
• 段落拆分：条目内的段落以「字符.字符」（无空格）为分隔特征，拆分时需保留前一段落末尾的句号

输入示例 #

input <- "1\tThis is a sentence. This is still part of the first paragraph.This is now the second paragraph.10\tThis is sentence number 1 of the tenth entry.This is the second sentence now. Still the second paragraph."

期望输出 #

[[1]]
[1] "1\tThis is a sentence. This is still part of the first paragraph."

[[2]]
[1] "This is now the second paragraph."

[[3]]
[1] "10\tThis is sentence number 1 of the tenth entry."

[[4]]
[1] "This is the second sentence now. Still the second paragraph."

解决方案 #

利用正则表达式的环视断言实现精准拆分，同时保留所需的分隔相关内容：

library(stringr)

input <- "1\tThis is a sentence. This is still part of the first paragraph.This is now the second paragraph.10\tThis is sentence number 1 of the tenth entry.This is the second sentence now. Still the second paragraph."

# 匹配两种拆分触发位置：句号后接条目编号（数字+制表符），或句号后接段落开头的大写字母
split_result <- str_split(input, "(?<=\\.)(?=\\d+\\t|[A-Z])")[[1]]

# 查看结果
split_result

正则逻辑解释 #

• (?<=\.)：正向回顾断言，确保拆分位置的前一个字符是句号，以此保留段落末尾的句号
• (?=\d+\t|[A-Z])：正向先行断言，匹配两种触发拆分的后续内容：
  • \d+\t：一串数字加制表符（新条目的开头）
  • [A-Z]：大写字母（新段落的开头）

内容的提问来源于stack exchange，提问作者Aaron