Flatten MultiIndex Groupby Results with reset_index() in Pandas

Question

After running `df.groupby(['region', 'category'])['revenue'].sum()`, the resulting Series has a MultiIndex. Convert it back into a flat DataFrame with clean column headers.

Accepted Answer

Optimal Solution:
import pandas as pd

# Method 1: as_index=False in groupby
flat_df = df.groupby(['region', 'category'], as_index=False)['revenue'].sum()

# Method 2: reset_index on existing MultiIndex object
# flat_df = grouped_series.reset_index(name='total_revenue')

Technical Explanation:
Using `as_index=False` in `groupby()` prevents the grouping columns from becoming the index. Alternatively, `.reset_index()` promotes index levels back to standard columns.

region	category	revenue
North	Electronics	45000
North	Fashion	32000

region	category	total_revenue
North	Electronics	45000
North	Fashion	32000