Python：拆分字符串时保留多个分隔符于原片段中

问题场景 #

给定字符串：

st = 'Walking happened at 8 am breakfast happened at 9am baseball happened at 12 pm lunch happened at 1pm'

需要以am或pm作为分隔符拆分字符串，且将这些分隔符保留在对应的原片段中，最终得到：

splitlist = ['Walking happened at 8 am',
             'breakfast happened at 9am',
             'baseball happened at 12 pm',
             'lunch happened at 1pm']

解决方案 #

常规拆分方法要么丢弃分隔符，要么会把分隔符单独作为列表项返回。这里可以借助Python的re模块，通过两种方式实现需求：

方案一：捕获分组拼接法

先通过正则拆分时捕获分隔符，再将相邻的内容片段与对应分隔符拼接：

import re

st = 'Walking happened at 8 am breakfast happened at 9am baseball happened at 12 pm lunch happened at 1pm'
parts = re.split(r'(am|pm)', st)
# 过滤空项并两两拼接内容与分隔符
splitlist = [''.join(parts[i:i+2]) for i in range(0, len(parts)-1, 2) if parts[i].strip()]

print(splitlist)

方案二：非贪婪匹配提取法

直接用正则匹配包含分隔符的完整片段，代码更简洁：

import re

st = 'Walking happened at 8 am breakfast happened at 9am baseball happened at 12 pm lunch happened at 1pm'
splitlist = re.findall(r'.*?(?:am|pm)', st)

print(splitlist)

方案说明 #

• 方案一通过re.split拆分时捕获am/pm，再把内容和分隔符重新组合，同时过滤拆分后可能出现的空字符串。
• 方案二用re.findall搭配非贪婪模式正则.*?(?:am|pm)，匹配任意字符直到遇到am或pm，直接提取包含分隔符的完整片段。

内容的提问来源于stack exchange，提问作者SantoshGupta7