ENH: is_scalar returns True for DateOffset objects

doc/source/whatsnew/v0.23.0.txt

@@ -144,6 +144,7 @@ Other Enhancements
 - :class:`Interval` and :class:`IntervalIndex` have gained a ``length`` attribute (:issue:`18789`)
 - ``Resampler`` objects now have a functioning :attr:`~pandas.core.resample.Resampler.pipe` method.
   Previously, calls to ``pipe`` were diverted to  the ``mean`` method (:issue:`17905`).
+- :func:`~pandas.api.types.is_scalar` now returns ``True`` for ``DateOffset`` objects (:issue:`18943`).
 
 .. _whatsnew_0230.api_breaking:
 

pandas/_libs/lib.pyx

@@ -112,6 +112,7 @@ cpdef bint isscalar(object val):
     - Period
     - instances of decimal.Decimal
     - Interval
+    - DateOffset
 
     """
 
@@ -126,7 +127,8 @@ cpdef bint isscalar(object val):
             or PyTime_Check(val)
             or util.is_period_object(val)
             or is_decimal(val)
-            or is_interval(val))
+            or is_interval(val)
+            or is_offset(val))
 
 
 def item_from_zerodim(object val):

pandas/_libs/src/inference.pyx

@@ -45,6 +45,8 @@ cpdef bint is_period(object val):
     """ Return a boolean if this is a Period object """
     return util.is_period_object(val)
 
+cdef inline bint is_offset(object val):
+    return getattr(val, '_typ', '_typ') == 'dateoffset'
 
 _TYPE_MAP = {
     'categorical': 'categorical',

pandas/tests/dtypes/test_inference.py

@@ -18,7 +18,8 @@
 from pandas._libs import tslib, lib, missing as libmissing
 from pandas import (Series, Index, DataFrame, Timedelta,
                     DatetimeIndex, TimedeltaIndex, Timestamp,
-                    Panel, Period, Categorical, isna)
+                    Panel, Period, Categorical, isna, Interval,
+                    DateOffset)
 from pandas.compat import u, PY2, PY3, StringIO, lrange
 from pandas.core.dtypes import inference
 from pandas.core.dtypes.common import (
@@ -1151,6 +1152,8 @@ def test_isscalar_pandas_scalars(self):
         assert is_scalar(Timestamp('2014-01-01'))
         assert is_scalar(Timedelta(hours=1))
         assert is_scalar(Period('2014-01-01'))
+        assert is_scalar(Interval(left=0, right=1))
+        assert is_scalar(DateOffset(days=1))
 
     def test_lisscalar_pandas_containers(self):
         assert not is_scalar(Series())