How to Match Multi-Line Text Blocks with Regular Expressions in Python?

Matching Multi-Line Text Blocks with Regular Expressions in Python

In Python, regex matching can be challenging when dealing with multi-line text. For example, consider the following text where "n" represents a newline:

some Varying TEXT

DSJFKDAFJKDAFJDSAKFJADSFLKDLAFKDSAF
[more of the above, ending with a newline]
[yep, there is a variable number of lines here]
[repeat the above a few hundred times].

The goal is to capture two elements:

• "some Varying TEXT"
• All lines of uppercase text starting two lines below the first element, as a single capture group (line breaks can be stripped out later).

Previous attempts using variations of the following regular expressions have been unsuccessful:

re.compile(r"^>(\w+)$$(\[.$]+)^$", re.MULTILINE)
re.compile(r"(^[^>]\[\w\s]+)$", re.MULTILINE|re.DOTALL)

Solution:

To match the multi-line text correctly, use the following regular expression:

re.compile(r"^(.+)\n((?:\n.+)+)", re.MULTILINE)

This pattern matches the following:

• Group 1: "some Varying TEXT"
• Group 2: All lines of uppercase text starting two lines below "some Varying TEXT"

Key Points:

• ^ and $ anchors match positions immediately after and before newlines, respectively.
• The ?: operator makes the newline group non-capturing.
• The .* quantifier captures one or more lines of uppercase text.

Alternative Solution:

If the target text may contain other types of newlines besides linefeeds (n), use the following more inclusive version:

re.compile(r"^(.+)(?:\n|\r\n?)((?:(?:\n|\r\n?).+)+)", re.MULTILINE)

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