(From master)

import pandas as pd

idx = pd.to_datetime(["2020-01-01", None]) idx.map(lambda x: pd.Timestamp("1999-01-01"), na_action="ignore")

DatetimeIndex(['1999-01-01', '1999-01-01'], dtype='datetime64[ns]', freq=None)

idx = pd.CategoricalIndex(["a", None], categories=["a"]) idx.map(lambda x: x, na_action="ignore")

TypeError: map() got an unexpected keyword argument 'na_action'

In the DatetimeIndex case idx.map should propagate the null value instead of returning Timestamp("1999-01-01") since na_action == "ignore", and although it isn't documented I think CategoricalIndex.map should allow na_action since the other map methods do.