BUG: PeriodEngine doesn't work (#29038)

Author: proost

pandas/core/indexes/period.py

@@ -17,6 +17,7 @@
     is_float_dtype,
     is_integer,
     is_integer_dtype,
+    is_period_arraylike,
     pandas_dtype,
 )
 
@@ -704,36 +705,38 @@ def get_loc(self, key, method=None, tolerance=None):
         -------
         loc : int
         """
+        if is_integer(key):
+            ordinal = key
+        else:
+            key = self._cast_to_period_object(key)
+            ordinal = iNaT if key is NaT else key.ordinal
+
         try:
-            return self._engine.get_loc(key)
+            if tolerance is not None:
+                tolerance = self._convert_tolerance(tolerance, np.asarray(key))
+            return self._int64index.get_loc(ordinal, method, tolerance)
         except KeyError:
-            if is_integer(key):
-                raise
+            raise KeyError(key)
 
+    def _cast_to_period_object(self, key):
+        if is_period_arraylike(key):
+            raise TypeError("'{val}' is an invalid key".format(val=key))
+        elif isinstance(key, str):
             try:
                 asdt, parsed, reso = parse_time_string(key, self.freq)
                 key = asdt
-            except TypeError:
-                pass
             except DateParseError:
                 # A string with invalid format
                 raise KeyError("Cannot interpret '{}' as period".format(key))
 
-            try:
-                key = Period(key, freq=self.freq)
-            except ValueError:
-                # we cannot construct the Period
-                # as we have an invalid type
-                raise KeyError(key)
-
-            try:
-                ordinal = iNaT if key is NaT else key.ordinal
-                if tolerance is not None:
-                    tolerance = self._convert_tolerance(tolerance, np.asarray(key))
-                return self._int64index.get_loc(ordinal, method, tolerance)
+        try:
+            key = Period(key, freq=self.freq)
+        except ValueError:
+            # we cannot construct the Period
+            # as we have an invalid type
+            raise KeyError(key)
 
-            except KeyError:
-                raise KeyError(key)
+        return key
 
     def _maybe_cast_slice_bound(self, label, side, kind):
         """

pandas/tests/indexes/common.py

@@ -331,7 +331,9 @@ def test_memory_usage(self, indices):
 
         # RangeIndex, IntervalIndex
         # don't have engines
-        if not isinstance(indices, (RangeIndex, IntervalIndex)):
+        # PeriodIndex
+        # don't use PeriodEngine with get_loc
+        if not isinstance(indices, (RangeIndex, IntervalIndex, PeriodIndex)):
             assert result2 > result
 
         if indices.inferred_type == "object":

pandas/tests/indexes/period/test_indexing.py

@@ -685,3 +685,32 @@ def test_period_index_indexer(self):
         tm.assert_frame_equal(df, df.loc[list(idx)])
         tm.assert_frame_equal(df.iloc[0:5], df.loc[idx[0:5]])
         tm.assert_frame_equal(df, df.loc[list(idx)])
+
+    def test_get_loc_not_use_engine(self):
+        # issue 29234
+        idx = PeriodIndex(
+            ["2014", "2015", "2016", "2017", np.datetime64("NaT")], freq="A"
+        )
+
+        pi = PeriodIndex(["2016"], freq="A")
+        msg = r"PeriodIndex\(\['2016'\], dtype='period\[A-DEC\]', freq='A-DEC'\)"
+        with pytest.raises(TypeError, match=msg):
+            idx.get_loc(pi)
+
+        ordinal = Period(2015, freq="A").ordinal
+        assert idx.get_loc(ordinal) == 1
+
+        with pytest.raises(KeyError, match="2015"):
+            idx.get_loc(2015)
+
+        with pytest.raises(KeyError, match="Cannot interpret 'foo-bar' as period"):
+            idx.get_loc("foo-bar")
+
+        assert idx.get_loc("2015-01-01") == 1
+
+        with pytest.raises(KeyError, match=r"\(2015, 2016\)"):
+            idx.get_loc((2015, 2016))
+
+        assert idx.get_loc(datetime(2016, 1, 1)) == 2
+
+        assert idx.get_loc(np.datetime64("NaT")) == 4