I am getting different results when using the where method with inplace=False vs inplace=True.

consider the following dataframe:

df = pd.DataFrame({'a':[1,None,3]}) df a 0 1.0 1 Nan 2 3.0 

when using the where method with inplace=False (the default), i get the following result:

df.where(pd.notnull(df), None) a 0 1.0 1 None 2 3.0

with a being converted to be of type object.

however if i do this:

df.where(pd.notnull(df), None, inplace=True) df a 0 1.0 1 Nan 2 3.0

a is of type float64

pandas version: 0.23.3 , numpy version: 1.14.5

reported because of my question on SO