How to groupby, then sort within groups in Pandas

How to groupby, then sort within groups in Pandas

To group by and then sort within groups in pandas, you can use the sort_values method after the groupby method.

The sort_values method allows you to specify the column to sort by, as well as the sorting order (ascending or descending).

Here is an example:

import pandas as pd

# create a sample dataframe
df = pd.DataFrame({'A': ['a', 'b', 'a', 'b'],
                   'B': [3, 2, 1, 4],
                   'C': [1, 2, 3, 4]})

# group by column A
grouped = df.groupby('A')

# sort the groups by column B in descending order
sorted_groups = grouped.apply(lambda x: x.sort_values('B', ascending=False))

# display the sorted groups
print(sorted_groups)

     A  B  C
A
a 0  a  3  1
  2  a  1  3
b 3  b  4  4
  1  b  2  2

This will group the data by column A and then sort each group by column B in descending order.

The resulting dataframe will have the same structure as the original dataframe, but the rows within each group will be sorted by the values in column B.