Automation of copy/paste from csv to a website

I'm looking for a Python developer to build a small, well-structured script that takes data from an Excel file and outputs it to CSV. The goal is a clean, reusable tool I can adapt to different files and column layouts in the future — not a one-off. What the script needs to do: Read data from an Excel file (.xlsx) and write the selected values out to CSV. Let me map which Excel columns map to which output fields through a simple configuration section at the top of the script (file paths, sheet name, column names), so I can reuse it without rewriting the logic. Clean the values as it goes: trim whitespace, skip empty cells, and remove duplicates so each value appears only once. Key requirements: Accuracy is critical. The values written out must match the source exactly — no truncation, no encoding issues (the data includes accented characters like á, é, í, ó, ñ), no dropped or altered rows. I'd like a quick validation step or count summary so I can confirm input vs. output match. Speed. It should process a few thousand rows quickly and run reliably end to end. Maintainable code. Clear structure, sensible function names, and short comments so I can modify it myself later. No hard-coded values buried in the logic — keep configuration separate. Deliverables: A single, documented Python script (.py). Brief instructions on how to run it and how to change the configuration for a new file. Nice to have: Basic error handling with clear messages if a column is missing or a file path is wrong.