Some arithmetic operators for IndexOpsMixin don't work with magic method.

Assuming that we have Series like the below.

>>> pser = pd.Series([1, 2, 3])
>>> kser = ks.from_pandas(pser)

and there is an issue for some cases with arithmetic ops like the below.

• rfloordiv

>>> pser.__rfloordiv__(pser)  # it's okay for pandas
0    1
1    1
2    1
Name: 0, dtype: int64

>>> kser.__rfloordiv__(kser)  # but doesn't work for koalas
Traceback (most recent call last):
...
TypeError: Column is not iterable

• rsub

>>> pser.__rsub__(pser)
0    0
1    0
2    0
Name: 0, dtype: int64

>>> kser.__rsub__(kser)
Traceback (most recent call last):
...
TypeError: Column is not iterable

I think there are more cases have same issue.

[itholic]

yes right. i just found them very coincidently, and also think it’s not so have high priority to solve for now.

[HyukjinKwon]

It might be better to fix anyway but I was wondering if it causes a real issue because these dunder methods are not supposed to called directly.