pydata/pandas — pull request #4779 by jreback (2013-09-09 01:51:08+00:00)
Title: TST/BUG: duplicate indexing ops with a Series using where and inplace add buggy (GH4550/GH4548)

closes #4550,#4548

```
In [1]: s = pd.concat([Series(list(range(3))),Series(list(range(3)))])

In [2]: s
Out[2]:
0 0
1 1
2 2
0 0
1 1
2 2
dtype: int64

In [3]: s.where(s<2)
Out[3]:
0 0
1 1
2 NaN
0 0
1 1
2 NaN
dtype: float64

In [4]: s[s<1] = 5

In [5]: s
Out[5]:
0 5
1 1
2 2
0 5
1 1
2 2
dtype: int64

In [6]: s[s<2] += 10

In [7]: s
Out[7]:
0 5
1 11
2 2
0 5
1 11
2 2
dtype: int64
```