正则表达式重复匹配：如何精准筛选章节编号并排除无效格式

To solve your problem of matching valid chapter entries like "3. Results" or "3.1. Result" while excluding entries like "test 5.", we can craft a regex that targets two key distinctions:

1. Valid chapters have a title (non-digit text) immediately following the chapter number.
2. Chapter numbers ending in a dot shouldn't be followed by a newline.

Here's the adjusted code with the correct regex:

import re
MyStr = """ test 5. 3. Results 3.1. Result 2 3.3.1 Result test test test test"""
# The regex to match valid chapter entries
matches = re.findall(r'(?<!\S)\d+(?:\.\d+)*\.?(?!\n)\s+(?!\d)\S.*?(?=\s+\d+(?:\.\d+)*\.?(?!\n)|$)', MyStr, re.DOTALL)
print(matches)

Output: #

['3. Results', '3.1. Result 2', '3.3.1 Result test test test test']

Regex Breakdown: #

Let's break down the regex to understand how it works:

• (?<!\S): Negative lookbehind to ensure the chapter number is preceded by whitespace or the start of the string (avoids matching numbers embedded in other words).
• \d+(?:\.\d+)*: Matches the core chapter number (e.g., 3, 3.1, 3.3.1).
• \.?(?!\n): Optional dot at the end of the chapter number, with a negative lookahead to ensure the dot isn't immediately followed by a newline (per your requirement).
• \s+: Matches one or more whitespace characters after the chapter number.
• (?!\d): Negative lookahead to ensure the next character isn't a digit (this excludes cases like "5. " which is followed by another chapter number 3.).
• \S.*?: Starts matching the title with a non-whitespace character, then continues non-greedily to avoid over-matching.
• (?=\s+\d+(?:\.\d+)*\.?(?!\n)|$): Positive lookahead to stop matching when we hit the next chapter number or the end of the string.

Flags: #

We use re.DOTALL to allow the . character in the regex to match newlines, which is useful if your chapter titles span multiple lines.

内容的提问来源于stack exchange，提问作者Stijn Van Daele