make TDI.get_value use get_loc, fix wrong-dtype NaT (#31230)

Author: jbrockmendel

pandas/core/arrays/timedeltas.py

@@ -44,10 +44,6 @@
 from pandas.tseries.offsets import Tick
 
 
-def _is_convertible_to_td(key):
-    return isinstance(key, (Tick, timedelta, np.timedelta64, str))
-
-
 def _field_accessor(name, alias, docstring=None):
     def f(self):
         values = self.asi8

pandas/core/indexes/timedeltas.py

@@ -1,5 +1,4 @@
 """ implement the TimedeltaIndex """
-from datetime import datetime
 
 import numpy as np
 
@@ -10,19 +9,23 @@
     _TD_DTYPE,
     is_float,
     is_integer,
-    is_list_like,
     is_scalar,
     is_timedelta64_dtype,
     is_timedelta64_ns_dtype,
     pandas_dtype,
 )
-from pandas.core.dtypes.missing import isna
+from pandas.core.dtypes.missing import is_valid_nat_for_dtype
 
 from pandas.core.accessor import delegate_names
 from pandas.core.arrays import datetimelike as dtl
-from pandas.core.arrays.timedeltas import TimedeltaArray, _is_convertible_to_td
+from pandas.core.arrays.timedeltas import TimedeltaArray
 import pandas.core.common as com
-from pandas.core.indexes.base import Index, _index_shared_docs, maybe_extract_name
+from pandas.core.indexes.base import (
+    Index,
+    InvalidIndexError,
+    _index_shared_docs,
+    maybe_extract_name,
+)
 from pandas.core.indexes.datetimelike import (
     DatetimeIndexOpsMixin,
     DatetimelikeDelegateMixin,
@@ -236,22 +239,10 @@ def get_value(self, series, key):
         Fast lookup of value from 1-dimensional ndarray. Only use this if you
         know what you're doing
         """
-
-        if isinstance(key, str):
-            try:
-                key = Timedelta(key)
-            except ValueError:
-                raise KeyError(key)
-
-        if isinstance(key, self._data._recognized_scalars) or key is NaT:
-            key = Timedelta(key)
-            return self.get_value_maybe_box(series, key)
-
-        value = Index.get_value(self, series, key)
-        return com.maybe_box(self, value, series, key)
-
-    def get_value_maybe_box(self, series, key: Timedelta):
-        loc = self.get_loc(key)
+        if is_integer(key):
+            loc = key
+        else:
+            loc = self.get_loc(key)
         return self._get_values_for_loc(series, loc)
 
     def get_loc(self, key, method=None, tolerance=None):
@@ -260,27 +251,31 @@ def get_loc(self, key, method=None, tolerance=None):
 
         Returns
         -------
-        loc : int
+        loc : int, slice, or ndarray[int]
         """
-        if is_list_like(key) or (isinstance(key, datetime) and key is not NaT):
-            # GH#20464 datetime check here is to ensure we don't allow
-            #   datetime objects to be incorrectly treated as timedelta
-            #   objects; NaT is a special case because it plays a double role
-            #   as Not-A-Timedelta
-            raise TypeError
-
-        if isna(key):
+        if not is_scalar(key):
+            raise InvalidIndexError(key)
+
+        if is_valid_nat_for_dtype(key, self.dtype):
             key = NaT
 
+        elif isinstance(key, str):
+            try:
+                key = Timedelta(key)
+            except ValueError:
+                raise KeyError(key)
+
+        elif isinstance(key, self._data._recognized_scalars) or key is NaT:
+            key = Timedelta(key)
+
+        else:
+            raise KeyError(key)
+
         if tolerance is not None:
             # try converting tolerance now, so errors don't get swallowed by
             # the try/except clauses below
             tolerance = self._convert_tolerance(tolerance, np.asarray(key))
 
-        if _is_convertible_to_td(key) or key is NaT:
-            key = Timedelta(key)
-            return Index.get_loc(self, key, method, tolerance)
-
         return Index.get_loc(self, key, method, tolerance)
 
     def _maybe_cast_slice_bound(self, label, side, kind):

pandas/core/indexing.py

@@ -1608,19 +1608,22 @@ def _convert_to_indexer(self, obj, axis: int, raise_missing: bool = False):
         is_int_index = labels.is_integer()
         is_int_positional = is_integer(obj) and not is_int_index
 
-        # if we are a label return me
-        try:
-            return labels.get_loc(obj)
-        except LookupError:
-            if isinstance(obj, tuple) and isinstance(labels, ABCMultiIndex):
-                if len(obj) == labels.nlevels:
-                    return {"key": obj}
-                raise
-        except TypeError:
-            pass
-        except ValueError:
-            if not is_int_positional:
-                raise
+        if is_scalar(obj) or isinstance(labels, ABCMultiIndex):
+            # Otherwise get_loc will raise InvalidIndexError
+
+            # if we are a label return me
+            try:
+                return labels.get_loc(obj)
+            except LookupError:
+                if isinstance(obj, tuple) and isinstance(labels, ABCMultiIndex):
+                    if len(obj) == labels.nlevels:
+                        return {"key": obj}
+                    raise
+            except TypeError:
+                pass
+            except ValueError:
+                if not is_int_positional:
+                    raise
 
         # a positional
         if is_int_positional:

pandas/tests/indexes/timedeltas/test_indexing.py

@@ -1,4 +1,5 @@
 from datetime import datetime, timedelta
+import re
 
 import numpy as np
 import pytest
@@ -48,12 +49,19 @@ def test_getitem(self):
 
     @pytest.mark.parametrize(
         "key",
-        [pd.Timestamp("1970-01-01"), pd.Timestamp("1970-01-02"), datetime(1970, 1, 1)],
+        [
+            pd.Timestamp("1970-01-01"),
+            pd.Timestamp("1970-01-02"),
+            datetime(1970, 1, 1),
+            pd.Timestamp("1970-01-03").to_datetime64(),
+            # non-matching NA values
+            np.datetime64("NaT"),
+        ],
     )
     def test_timestamp_invalid_key(self, key):
         # GH#20464
         tdi = pd.timedelta_range(0, periods=10)
-        with pytest.raises(TypeError):
+        with pytest.raises(KeyError, match=re.escape(repr(key))):
             tdi.get_loc(key)