>>df ABCD E 0 0 0 0 F 0 0 0 0 G 0 0 0 0 H 0 0 0 0

It is necessary to change the cell df[A][E] .
Using df[A][E] = 2 leads to a warning.

    1 answer 1

    Use DataFrame.loc[<index_slice>, <column_slice>] :

     In [7]: df.loc['E','A'] = 111 In [8]: df Out[8]: ABCD E 111 0 0 0 F 0 0 0 0 G 0 0 0 0 H 0 0 0 0

    or DataFrame.at[...] :

     In [10]: df.at['E', 'A'] = 222 In [11]: df Out[11]: ABCD E 222 0 0 0 F 0 0 0 0 G 0 0 0 0 H 0 0 0 0