2. Multi-Level Group By

A multi-level groupby in Pandas refers to grouping data by multiple columns, where each group is determined by a combination of values from multiple columns. This allows for more granular aggregation and can be used to perform complex analyses on hierarchical or nested data.

Multi-Index

When you group by more than one column, Pandas creates a MultiIndex (a hierarchical index) that allows you to access and manipulate data at different levels.

df.groupby(['list', 'of', 'columns', 'to', 'groupby']).agg_func()

See also group by aggregation functions