Standardize Column Names and Clean Headers in Pandas

Question

Given a DataFrame with messy column headers like `[' Customer ID ', 'Order-Date!!', 'Total Amount ($)']`, normalize them all into clean lowercase `snake_case` without special characters.

Accepted Answer

Optimal Solution:
import re
import pandas as pd

def clean_columns(df: pd.DataFrame) -> pd.DataFrame:
    df.columns = [
        re.sub(r'[^a-z0-9_]', '', col.strip().lower().replace(' ', '_').replace('-', '_'))
        for col in df.columns
    ]
    return df

Technical Explanation:
List comprehension on `df.columns` strips whitespace, lowercases text, replaces spaces with underscores, and strips illegal characters.