How to Match Multiline Blocks in Python Using Regular Expressions?

Matching Multiline Blocks Using Regular Expressions

You may encounter difficulties when matching against text that spans multiple lines using Python's regular expressions. Consider the following example text:

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 components:

• "some Varying TEXT"
• All uppercase lines located two lines beneath it (excluding any newline characters)

Several approaches have been attempted unsuccessfully:

<code class="python">re.compile(r"^>(\w+)$$(\n[.$]+)^$", re.MULTILINE) # Capture both parts
re.compile(r"([^>][\w\s]+)$", re.MULTILINE|re.DOTALL) # Just textlines</code>

To address this issue, utilize the following regular expression:

<code class="python">re.compile(r"^(.+)\n((?:\n.+)+)", re.MULTILINE)</code>

Keep in mind that anchors "^" and "$" do not match linefeeds. Hence, in multiline mode, "^" follows a newline, and "$" precedes a newline.

Furthermore, be mindful of various newline formats. For text that may contain linefeeds, carriage-returns, or both, employ this more inclusive regex:

<code class="python">re.compile(r"^(.+)(?:\n|\r\n?)((?:(?:\n|\r\n?).+)+)", re.MULTILINE)</code>

The DOTALL modifier is unnecessary here because the dot already excludes newlines.

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