How to preprocess excel sheets with multi-level headers and sections for API Input?

API
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1

I’m working with Excel files that use a combination of:

  1. Multi-row column headers (e.g., dates in one row, week labels in the next).
  2. Side headers with section titles and sub-rows (like a grouped report: A → A1, A2, etc, B → B1, B2)
  3. Formatting variations across sheets (different number of header rows, different styles, etc)

Each sheet may follow a different layout, but they share similar structural ideas (sectioned rows, nested headers). I’d like to flatten and normalize these sheets into JSON or structured tabular data for API submission.

What are the best practices to achieve this?

  • I need my gpt to use the numbers I provided to generate accurate narrative. If I skip the data preparation step and attach the whole excel, it’s misleading the numbers. So, I need the preprocessing step for the GPT to just use accurate numbers.

Something like this:

        | 6/30 | 7/7 | … |
        | W5 | W6 | … | .|
| A
|   A1
|   A2
| B
|   B1
|   B2