Add level to a MultiIndexes in pandas

Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

import numpy as np
import pandas as pd
from numpy.random import randn

from beakerx import beakerx, TableDisplay

beakerx.pandas_display_default()

df = pd.DataFrame(
    {"month": [1, 4, 7, 10], "year": [2012, 2014, 2013, 2014], "sale": [55, 40, 84, 31]}
)
df

Add a Level to Row Index¶

df2 = pd.concat([df], keys=["Foo"], names=["Firstlevel"])
df2

df2.index

MultiIndex(levels=[['Foo'], [0, 1, 2, 3]],
           labels=[[0, 0, 0, 0], [0, 1, 2, 3]],
           names=['Firstlevel', None])

df2.columns

Index(['month', 'year', 'sale'], dtype='object')

df3 = pd.concat([df], keys=["Foo"], names=["Firstlevel"], axis=1)
df3

df3.columns

MultiIndex(levels=[['Foo'], ['month', 'year', 'sale']],
           labels=[[0, 0, 0], [0, 1, 2]],
           names=['Firstlevel', None])

df3.index

RangeIndex(start=0, stop=4, step=1)