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Automatically Highlight Data Validation Errors Inside Excel Files in Python

Load an Excel file with openpyxl, iterate over cells, and highlight invalid data (empty, negative) with a red fill and error message.

excel validation openpyxl

Python

import openpyxl
from openpyxl.styles import PatternFill
from pathlib import Path

def highlight_validation_errors(filepath: str, output_path: str = None):
    wb = openpyxl.load_workbook(filepath)
    red_fill = PatternFill(start_color="FF0000", end_color="FF0000", fill_type="solid")
    
    for sheet in wb.worksheet…

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