BUG: loc.__setitem__ over MultiIndex with slice key and step != 1 does strange things #8856
Description
Here's how it looks like:
In [11]: s = pd.Series(np.arange(10), pd.MultiIndex.from_product(([0, 1], list('abcde')))) In [12]: s Out[12]: 0 a 0 0 b 1 0 c 2 0 d 3 0 e 4 1 a 5 1 b 6 1 c 7 1 d 8 1 e 9 dtype: int64 In [13]: s.iloc[::4] = 100; s Out[13]: 0 a 100 0 b 100 0 c 100 0 d 100 0 e 100 1 a 5 1 b 6 1 c 7 1 d 8 1 e 9 dtype: int64 In [14]: s.loc[::4] = 200; s Out[14]: 0 a 200 0 b 200 0 c 200 0 d 200 0 e 200 1 a 5 1 b 6 1 c 7 1 d 8 1 e 9 dtype: int64 In [15]: s.ix[::4] = 300; s Out[15]: 0 a 300 0 b 300 0 c 300 0 d 300 0 e 300 1 a 5 1 b 6 1 c 7 1 d 8 1 e 9 dtype: int64Regular setitem works fine:
In [16]: s[::4] = 10000; s Out[16]: 0 a 10000 0 b 300 0 c 300 0 d 300 0 e 10000 1 a 5 1 b 6 1 c 7 1 d 10000 1 e 9 dtype: int64I have some ideas about iloc refactoring that will fix that for iloc, but loc/ix will still be affected.