dtype changes after set_value/at
I think the problem is related to the fact that I was trying to assign a None to a bool Series, then it just tries to convert to a different type (why not object?)
Fixed changing the dtype to object first: dataframe.foo = dataframe.foo.astype(object).
Works like a charm now.
I'm facing a weird issue on Pandas now, not sure if a pandas pitfall or just something I'm missing...
My pd.Series is just
foo
False
False
False

> a.foo.dtype
dtype('bool')

When I use a dataframe.set_value(index, col, None), my whole Series is converted to dtype('float64') (same thing applies to a.at[index, col] = None).
Now my Series is

foo
NaN
NaN
NaN

Do you have any idea on how this happens and how to fix it?
Thanks in advance. :)
Edit:
Using 0.20.1.