REF: make PeriodIndex.get_value wrap PeriodIndex.get_loc (#31318)

Author: jbrockmendel

pandas/core/indexes/period.py

@@ -1,5 +1,5 @@
 from datetime import datetime, timedelta
-from typing import Any
+from typing import TYPE_CHECKING, Any
 import weakref
 
 import numpy as np
@@ -20,6 +20,7 @@
     is_integer_dtype,
     is_list_like,
     is_object_dtype,
+    is_scalar,
     pandas_dtype,
 )
 
@@ -33,6 +34,7 @@
 import pandas.core.common as com
 import pandas.core.indexes.base as ibase
 from pandas.core.indexes.base import (
+    InvalidIndexError,
     _index_shared_docs,
     ensure_index,
     maybe_extract_name,
@@ -52,6 +54,8 @@
 _index_doc_kwargs = dict(ibase._index_doc_kwargs)
 _index_doc_kwargs.update(dict(target_klass="PeriodIndex or list of Periods"))
 
+if TYPE_CHECKING:
+    from pandas import Series
 
 # --- Period index sketch
 
@@ -479,43 +483,16 @@ def inferred_type(self) -> str:
         # indexing
         return "period"
 
-    def get_value(self, series, key):
+    def get_value(self, series: "Series", key):
         """
         Fast lookup of value from 1-dimensional ndarray. Only use this if you
         know what you're doing
         """
         if is_integer(key):
-            return series.iat[key]
-
-        if isinstance(key, str):
-            try:
-                loc = self._get_string_slice(key)
-                return series[loc]
-            except (TypeError, ValueError, OverflowError):
-                pass
-
-            asdt, reso = parse_time_string(key, self.freq)
-            grp = resolution.Resolution.get_freq_group(reso)
-            freqn = resolution.get_freq_group(self.freq)
-
-            # _get_string_slice will handle cases where grp < freqn
-            assert grp >= freqn
-
-            if grp == freqn:
-                key = Period(asdt, freq=self.freq)
-                loc = self.get_loc(key)
-                return series.iloc[loc]
-            else:
-                raise KeyError(key)
-
-        elif isinstance(key, Period) or key is NaT:
-            ordinal = key.ordinal if key is not NaT else NaT.value
-            loc = self._engine.get_loc(ordinal)
-            return series[loc]
-
-        # slice, PeriodIndex, np.ndarray, List[Period]
-        value = Index.get_value(self, series, key)
-        return com.maybe_box(self, value, series, key)
+            loc = key
+        else:
+            loc = self.get_loc(key)
+        return self._get_values_for_loc(series, loc)
 
     @Appender(_index_shared_docs["get_indexer"] % _index_doc_kwargs)
     def get_indexer(self, target, method=None, limit=None, tolerance=None):
@@ -571,6 +548,9 @@ def get_loc(self, key, method=None, tolerance=None):
             If key is listlike or otherwise not hashable.
         """
 
+        if not is_scalar(key):
+            raise InvalidIndexError(key)
+
         if isinstance(key, str):
 
             try:

pandas/tests/indexes/period/test_indexing.py

@@ -1,4 +1,5 @@
 from datetime import datetime, timedelta
+import re
 
 import numpy as np
 import pytest
@@ -8,6 +9,7 @@
 import pandas as pd
 from pandas import DatetimeIndex, Period, PeriodIndex, Series, notna, period_range
 import pandas._testing as tm
+from pandas.core.indexes.base import InvalidIndexError
 
 
 class TestGetItem:
@@ -408,11 +410,7 @@ def test_get_loc(self):
         with pytest.raises(KeyError, match=r"^1\.1$"):
             idx0.get_loc(1.1)
 
-        msg = (
-            r"'PeriodIndex\(\['2017-09-01', '2017-09-02', '2017-09-03'\], "
-            r"dtype='period\[D\]', freq='D'\)' is an invalid key"
-        )
-        with pytest.raises(TypeError, match=msg):
+        with pytest.raises(InvalidIndexError, match=re.escape(str(idx0))):
             idx0.get_loc(idx0)
 
         # get the location of p1/p2 from
@@ -433,11 +431,7 @@ def test_get_loc(self):
         with pytest.raises(KeyError, match=r"^1\.1$"):
             idx1.get_loc(1.1)
 
-        msg = (
-            r"'PeriodIndex\(\['2017-09-02', '2017-09-02', '2017-09-03'\], "
-            r"dtype='period\[D\]', freq='D'\)' is an invalid key"
-        )
-        with pytest.raises(TypeError, match=msg):
+        with pytest.raises(InvalidIndexError, match=re.escape(str(idx1))):
             idx1.get_loc(idx1)
 
         # get the location of p1/p2 from
@@ -461,16 +455,46 @@ def test_get_loc_integer(self):
         with pytest.raises(KeyError, match="46"):
             pi2.get_loc(46)
 
+    @pytest.mark.parametrize("freq", ["H", "D"])
+    def test_get_value_datetime_hourly(self, freq):
+        # get_loc and get_value should treat datetime objects symmetrically
+        dti = pd.date_range("2016-01-01", periods=3, freq="MS")
+        pi = dti.to_period(freq)
+        ser = pd.Series(range(7, 10), index=pi)
+
+        ts = dti[0]
+
+        assert pi.get_loc(ts) == 0
+        assert pi.get_value(ser, ts) == 7
+        assert ser[ts] == 7
+        assert ser.loc[ts] == 7
+
+        ts2 = ts + pd.Timedelta(hours=3)
+        if freq == "H":
+            with pytest.raises(KeyError, match="2016-01-01 03:00"):
+                pi.get_loc(ts2)
+            with pytest.raises(KeyError, match="2016-01-01 03:00"):
+                pi.get_value(ser, ts2)
+            with pytest.raises(KeyError, match="2016-01-01 03:00"):
+                ser[ts2]
+            with pytest.raises(KeyError, match="2016-01-01 03:00"):
+                ser.loc[ts2]
+        else:
+            assert pi.get_loc(ts2) == 0
+            assert pi.get_value(ser, ts2) == 7
+            assert ser[ts2] == 7
+            assert ser.loc[ts2] == 7
+
     def test_get_value_integer(self):
         dti = pd.date_range("2016-01-01", periods=3)
         pi = dti.to_period("D")
         ser = pd.Series(range(3), index=pi)
-        with pytest.raises(IndexError, match="is out of bounds for axis 0 with size 3"):
+        with pytest.raises(IndexError, match="index out of bounds"):
             pi.get_value(ser, 16801)
 
         pi2 = dti.to_period("Y")  # duplicates, ordinals are all 46
         ser2 = pd.Series(range(3), index=pi2)
-        with pytest.raises(IndexError, match="is out of bounds for axis 0 with size 3"):
+        with pytest.raises(IndexError, match="index out of bounds"):
             pi2.get_value(ser2, 46)
 
     def test_is_monotonic_increasing(self):
@@ -544,25 +568,25 @@ def test_get_value(self):
         p2 = pd.Period("2017-09-03")
 
         idx0 = pd.PeriodIndex([p0, p1, p2])
-        input0 = np.array([1, 2, 3])
+        input0 = pd.Series(np.array([1, 2, 3]), index=idx0)
         expected0 = 2
 
         result0 = idx0.get_value(input0, p1)
         assert result0 == expected0
 
         idx1 = pd.PeriodIndex([p1, p1, p2])
-        input1 = np.array([1, 2, 3])
-        expected1 = np.array([1, 2])
+        input1 = pd.Series(np.array([1, 2, 3]), index=idx1)
+        expected1 = input1.iloc[[0, 1]]
 
         result1 = idx1.get_value(input1, p1)
-        tm.assert_numpy_array_equal(result1, expected1)
+        tm.assert_series_equal(result1, expected1)
 
         idx2 = pd.PeriodIndex([p1, p2, p1])
-        input2 = np.array([1, 2, 3])
-        expected2 = np.array([1, 3])
+        input2 = pd.Series(np.array([1, 2, 3]), index=idx2)
+        expected2 = input2.iloc[[0, 2]]
 
         result2 = idx2.get_value(input2, p1)
-        tm.assert_numpy_array_equal(result2, expected2)
+        tm.assert_series_equal(result2, expected2)
 
     def test_get_indexer(self):
         # GH 17717