Python Data Entry Automation Script

I need a straightforward Python script that fully automates a repetitive data-entry routine I currently handle by hand. The job is purely about automation—no web scraping or complex analytics—so the focus is on taking raw data I receive and placing it into the correct structure without manual copying or pasting.

Here’s what I have in mind:
• The script reads an incoming data source (most often CSV or XLSX, though I’m open to suggestions)
• It maps each field to the destination layout I’ll provide
• Basic validation flags missing or mis-typed values before the final file is produced
• The finished output is an updated spreadsheet or database-ready file I can use immediately

Please write it in clean, well-commented Python. Standard libraries are fine, though pandas or openpyxl would speed things up, and I want to be able to run it from the command line on Windows without extra configuration hassles.

Deliverables
1. The .py script, fully commented
2. A short README with setup and usage instructions
3. Any sample config or mapping file if your approach requires one

Acceptance criteria
– I can point the script at a sample data file and, with one command, receive a correctly filled template in under a minute
– No data loss or column mismatch after validation
– Clear error messages when a record fails validation

If you’ve built similar data-entry automation before, let me know. I’ll share a sample file and template as soon as we start.