Option to Raise Exception on Unmapped Value in Series.map

[cancan101]

Add a flag (or extend na_action) to raise an exception in Series.map if a value is not successfully mapped (ie in the case where arg is a dict.

[jreback]

I am not sure what the intent / meaning of this parameter. @cancan101 can you give an example?

[cancan101]

If I were do this:

Series(['a', 'b']).map({'a': 1, 'b': 3})

my return type is of int64 and everything is mapped.
However for this:

Series(['a', 'b ']).map({'a': 1, 'b': 3}) # note space

my return type is floatX and there is a nan. Instead this is a "mistake" and I would have preferred an exception to be raised.

I could assert that the type is int (brittle and just works for ints) or perhaps check all of the unique values in advance to make sure they are a subset of the mapping arg keys (require another pass over data).

[TomAugspurger]

Related (but different from) #13473

I'd be in favor of adding a 'raise' option when there's a value in the series that doesn't get mapped.

Does anyone know what the na_action parameter actually does? The docs aren't that clear and I can't figure it out with simple testing. Is this controlling NA values in the original series, or the output? Ideally we'd use the errors={'ignore', 'raise'} keyword we're using elsewhere, and deprecate na_action (if it's doing what I think it is).

[cancan101]

@TomAugspurger Funny you should ask: http://stackoverflow.com/questions/39461328/in-pandas-what-does-the-na-action-parameter-to-series-map-do/39461948#39461948

[bollard]

Quite the 6-year necroraise, but little bump that would be really useful to have an na_action="raise" on Series.map

A workaround for the moment is to (re)define __missing__ to raise, i.e.

class WillRaise(dict):
    def __missing__(self, key):
        raise KeyError(key)

mapping = WillRaise({"Foo": 1})
pd.Series(["Foo", "Bar"]).map(mapping) # KeyError: 'Bar'

[IPerezGonzalez]

Hi all,
I find myself with the same need as @cancan101 some years ago: optionally raise an error when a value does not get mapped. It does not look like this has been implemented yet. Are there any plans?
Irene