add index column pandas code example

Example 1: pandas create a column from index

df.reset_index(level=0, inplace=True)

Example 2: how to change indeces in pandas dataframe

>>> df.set_index('month')
       year  sale
month
1      2012    55
4      2014    40
7      2013    84
10     2014    31

Example 3: add an index column pandas

import numpy as np
import pandas as pd
df = pd.DataFrame({'month': [2, 5, 8, 10],
                   'year': [2017, 2019, 2018, 2019],
                   'sale': [60, 45, 90, 36]})
df.set_index('month')