i lost my second column in groupby by two columns code example

Example 1: python - gropuby based on 2 variabels

df.groupby(['col5', 'col2']).size()

Example 2: group by 2 columns pandas

In [11]: df.groupby(['col5', 'col2']).size()
Out[11]:
col5  col2
1     A       1
      D       3
2     B       2
3     A       3
      C       1
4     B       1
5     B       2
6     B       1
dtype: int64