allow DatetimeArray._scalar_from_string to return NaT for blank string

Author: jhendricks487

doc/source/whatsnew/v3.0.0.rst

@@ -446,6 +446,7 @@ Other Deprecations
 - Deprecated allowing non-keyword arguments in :meth:`Series.to_string` except ``buf``. (:issue:`57280`)
 - Deprecated behavior of :meth:`.DataFrameGroupBy.groups` and :meth:`.SeriesGroupBy.groups`, in a future version ``groups`` by one element list will return tuple instead of scalar. (:issue:`58858`)
 - Deprecated behavior of :meth:`Series.dt.to_pytimedelta`, in a future version this will return a :class:`Series` containing python ``datetime.timedelta`` objects instead of an ``ndarray`` of timedelta; this matches the behavior of other :meth:`Series.dt` properties. (:issue:`57463`)
+- Deprecated empty string in :class:`Timestamp` (:issue:`61149`)
 - Deprecated lowercase strings ``d``, ``b`` and ``c`` denoting frequencies in :class:`Day`, :class:`BusinessDay` and :class:`CustomBusinessDay` in favour of ``D``, ``B`` and ``C`` (:issue:`58998`)
 - Deprecated lowercase strings ``w``, ``w-mon``, ``w-tue``, etc. denoting frequencies in :class:`Week` in favour of ``W``, ``W-MON``, ``W-TUE``, etc. (:issue:`58998`)
 - Deprecated parameter ``method`` in :meth:`DataFrame.reindex_like` / :meth:`Series.reindex_like` (:issue:`58667`)

pandas/_libs/tslibs/timestamps.pyx

@@ -2657,6 +2657,13 @@ class Timestamp(_Timestamp):
                 tzinfo is None):
             return ts_input
         elif isinstance(ts_input, str):
+            if ts_input == "":
+                warnings.warn(
+                    "Passing an empty string to Timestamp is deprecated and will raise "
+                    "a ValueError in a future version. Use `pd.NaT` directly instead.",
+                    FutureWarning,
+                    stacklevel = find_stack_level()
+                )
             # User passed a date string to parse.
             # Check that the user didn't also pass a date attribute kwarg.
             if any(arg is not None for arg in _date_attributes):

pandas/core/arrays/datetimes.py

@@ -547,6 +547,8 @@ def _unbox_scalar(self, value) -> np.datetime64:
             return value.as_unit(self.unit, round_ok=False).asm8
 
     def _scalar_from_string(self, value) -> Timestamp | NaTType:
+        if value == "":
+            value = NaT
         return Timestamp(value, tz=self.tz)
 
     def _check_compatible_with(self, other) -> None:

pandas/tests/scalar/test_nat.py

@@ -109,7 +109,13 @@ def test_nat_vector_field_access():
     "value", [None, np.nan, iNaT, float("nan"), NaT, "NaT", "nat", "", "NAT"]
 )
 def test_identity(klass, value):
-    assert klass(value) is NaT
+    if value == "" and klass == Timestamp:
+        msg = "Passing an empty string to Timestamp"
+        with tm.assert_produces_warning(FutureWarning, match=msg):
+            result = klass(value)
+    else:
+        result = klass(value)
+    assert result is NaT
 
 
 @pytest.mark.parametrize("klass", [Timestamp, Timedelta])

pandas/tests/scalar/timestamp/test_constructors.py

@@ -62,6 +62,11 @@ def test_constructor_float_not_round_with_YM_unit_raises(self):
         with pytest.raises(ValueError, match=msg):
             Timestamp(150.5, unit="M")
 
+    def test_constructor_with_empty_string(self):
+        msg = "Passing an empty string to Timestamp"
+        with tm.assert_produces_warning(FutureWarning, match=msg):
+            Timestamp("")
+
     @pytest.mark.parametrize(
         "value, check_kwargs",
         [