I am new to pandas and I can add to cumsum as

`df.cumsum(axis=1)`

```
   y0  y1  y2
0   2   3   4
1   2   2   3
2   0   0   0
3   1   2   3
   y0  y1  y2
0   2   5   9
1   2   4   7
2   0   0   0
3   1   3   6

```

But is there way to perform on only first 2 columns i.e. skip y2?