Change df.columns.names for multiindex columns

Question

I would like to rename one of my levels in a multiindexed columns dataframe in pandas.

df.columns.names

gives me

FrozenList(['level0', 'level1'])

I want to rename 'level0' to 'main'.

I have tried different approaches, none works:

 df.columns.set_names('findingkey', level=0, inplace=True)

gives me TypeError: 'list' object is not callable

I also tried to do it directly:

df.columns.names[0]='main'

with output: TypeError: 'FrozenList' does not support mutable operations.

user_2901002 · Answer

Use:

df.columns.names = ['main', 'level1']

Or

df = df.rename_axis(['main', 'level1'], axis=1)