Creating a column with sum of multiple columns grouped by name in panda

I have a dataset and I need to get the sum from two other columns and group them by name.

DF

 a       b        c
Joe      1        0
Joe      1        0
Joe      0        1
Adam     1        0
Adam     0        1
Adam     0        0

Desired Output:

  a        b      c       d
 Joe       1      0       1
 Joe       1      0       2
 Joe       0      1       3
 Adam      1      0       1
 Adam      0      1       2
 Adam      0      0       2 

I have tried df['d'] = df.groupby('a')['b','c'].sum()

When I do this I get NaN as a result.

>Solution :

You need to do a cumulative sum grouped on that column.
Something like this should work

df['sum'] = df['b'] + df['c']
df['d'] = df.groupby('a')['sum'].cumsum()

which gives

a       b    c  sum d
0   Joe 1   0   1   1
1   Joe 1   0   1   2
2   Joe 0   1   1   3
3   Adam 1  0   1   1
4   Adam 0  1   1   2
5   Adam 0  0   0   2