sort by two columns in pandas

df.sort_values(['a', 'b'], ascending=[True, False])

Here is what the above code is Doing:
1. Sort the DataFrame by column ‘a’, in ascending order (default).
2. Sort the DataFrame by column ‘b’, in descending order.
3. Sort the DataFrame by column ‘a’, then by column ‘b’, in ascending order.
4. Sort the DataFrame by column ‘a’, then by column ‘b’, in descending order.