no your example was fine, maybe something that uses integers or something? just a pure Series (before you do the DataFrame example)

```
In [2]: s = Series(np.arange(10),index=np.arange(10)[::-1],dtype='int64')

In [3]: s
Out[3]: 
9    0
8    1
7    2
6    3
5    4
4    5
3    6
2    7
1    8
0    9
dtype: int64

In [5]: s[s.isin([2,4])]
Out[5]: 
7    2
5    4
dtype: int64
```