Storing / Working With Large Text Blocks to Be Inserted Into Documents in Python

Question

I work in Python and have to generate spreadsheets frequently to share my data with programming-naive colleagues. I embed large blocks of text explaining the contents of the spreadsheet and how it was generated into the first page of these spreadsheets routinely. I don't like relying on an associated document to explain definitions, criteria, algorithms, and reliability when I send my results out into the world.

It's really awkward to edit and store the long strings that make up these blocks of text. I'd love to store them in dedicated files that I can work with using a tool INTENDED to edit large blocks of text. I'm wondering how other people deal with this kind of situation. JSON files? YAML? Some obvious built-in functionality in Python I don't know about?

This is obviously a very open-ended question. I'm sure there a lot of different approaches and solutions out there. It's a difficult thing to search for online as there are a lot of obfuscating factors when you search for things like 'python large strings' or 'python text files'. I'm hoping to hear about a number of different approaches.