Pandas in Action

9 The GroupBy object

This chapter covers

• Splitting a DataFrame into groups by using the groupby method
• Extracting first and last rows from groups in a GroupBy object
• Performing aggregate operations on GroupBy groups
• Iterating over DataFrames in a GroupBy object

The pandas library’s GroupBy object is a storage container for grouping DataFrame rows into buckets. It provides a set of methods to aggregate and analyze each independent group in the collection. It allows us to extract rows at specific index positions within each group. It also offers a convenient way to iterate over the groups of rows. There’s lots of power packed into a GroupBy object, so let’s see what it’s capable of doing.

9.1 Creating a GroupBy object from scratch

Let’s create ...