setting index in pandas code example

Example 1: set index to column pandas

df = df.set_index('col')
df['col'] = df.index

Example 2: how to set index pandas

# assignment copy
df = df.set_index('month')

# or inplace
df.set_index('month', inplace=True)

#      year   sale  month            month  year   sale
#  0   2012   55    1                1      2012   55
#  1   2014   40    4       =>       4      2014   40
#  2   2013   84    7                7      2013   84
#  3   2014   31    10               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')

Example 4: how to change indeces in pandas dataframe

>>> df = pd.DataFrame({'month': [1, 4, 7, 10],
...                    'year': [2012, 2014, 2013, 2014],
...                    'sale': [55, 40, 84, 31]})
>>> df
   month  year  sale
0      1  2012    55
1      4  2014    40
2      7  2013    84
3     10  2014    31