df unpdate index code example

Example 1: 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 2: change dataframe value by index

x    y
A  NaN  NaN
B  NaN  NaN
C  NaN  NaN

df.at['C', 'x'] = 10