How to Split Text on Markup in Python Using Regex

Discover how to tokenize markup text efficiently using regex in Python while avoiding common pitfalls.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Split text on markup in Python

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Split Text on Markup in Python Using Regex

Parsing and tokenizing markup text can be quite challenging, especially when our data contains both HTML/XML-like tags and plain text elements. You've come across a situation where you're attempting to split a line of text to isolate markup tags and content, yet the approach you've taken returns unwanted results. In this guide, we will address this common problem and examine a more efficient solution for achieving the desired outcome.

The Problem: Splitting Markup Text

Let's consider the following example of text containing markup:

[[See Video to Reveal this Text or Code Snippet]]

You want to break this down into a list that will yield the following structure:

[[See Video to Reveal this Text or Code Snippet]]

You initially attempted to use Python's re module with a regular expression, but the result included unwanted elements due to capturing groups in your regex pattern. Specifically, the closing tags were added to the result list because they were captured within the regex operation.

A More Effective Solution: Regex as a Tokenizer

Here’s how to do it:

Step-by-Step Tokenization Using Regex

Utilize Non-Capturing Groups: Instead of capturing specific groups, we will use non-capturing groups to avoid unwanted matches.

Construct the Regex: You can create a regex pattern that matches either valid markup tags or plain text sections.

The Revised Code

Here’s a concise way to achieve this:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Regex Pattern

Non-Capturing Group: The use of (?:...) allows us to group part of the regex without capturing it for return.

Tag Matching: The expression <(?:.*?>)? matches any opening markup tag effectively.

Plain Text Matching: The [^<]+ matches any sequence of characters that are not a <, which allows us to capture non-tag content.

Output Verification

Running this code will yield you the correctly tokenized list as desired:

[[See Video to Reveal this Text or Code Snippet]]

Final Thoughts

Using regex for simple text tokenization can be incredibly effective when done right. However, remember that for more complex HTML parsing—especially where attributes or nested tags are involved—consider using a dedicated HTML parsing library, like BeautifulSoup or lxml, which are built to handle such intricacies effectively.

By following these steps, you can achieve clean and organized tokenization of markup without the fuss of unwanted captures. Happy coding!