BUG: TimedeltaArray+Period, PeriodArray-TimedeltaArray (#33883)

Author: jbrockmendel

doc/source/whatsnew/v1.1.0.rst

@@ -647,6 +647,7 @@ Datetimelike
 - :meth:`DataFrame.min`/:meth:`DataFrame.max` not returning consistent result with :meth:`Series.min`/:meth:`Series.max` when called on objects initialized with empty :func:`pd.to_datetime`
 - Bug in :meth:`DatetimeIndex.intersection` and :meth:`TimedeltaIndex.intersection` with results not having the correct ``name`` attribute (:issue:`33904`)
 - Bug in :meth:`DatetimeArray.__setitem__`, :meth:`TimedeltaArray.__setitem__`, :meth:`PeriodArray.__setitem__` incorrectly allowing values with ``int64`` dtype to be silently cast (:issue:`33717`)
+- Bug in subtracting :class:`TimedeltaIndex` from :class:`Period` incorrectly raising ``TypeError`` in some cases where it should succeed and ``IncompatibleFrequency`` in some cases where it should raise ``TypeError`` (:issue:`33883`)
 
 Timedelta
 ^^^^^^^^^

pandas/core/arrays/datetimelike.py

@@ -1190,6 +1190,10 @@ def _sub_period(self, other):
         # Overridden by PeriodArray
         raise TypeError(f"cannot subtract Period from a {type(self).__name__}")
 
+    def _add_period(self, other: Period):
+        # Overriden by TimedeltaArray
+        raise TypeError(f"cannot add Period to a {type(self).__name__}")
+
     def _add_offset(self, offset):
         raise AbstractMethodError(self)
 
@@ -1364,6 +1368,8 @@ def __add__(self, other):
             result = self._add_offset(other)
         elif isinstance(other, (datetime, np.datetime64)):
             result = self._add_datetimelike_scalar(other)
+        elif isinstance(other, Period) and is_timedelta64_dtype(self.dtype):
+            result = self._add_period(other)
         elif lib.is_integer(other):
             # This check must come after the check for np.timedelta64
             # as is_integer returns True for these

pandas/core/arrays/period.py

@@ -32,7 +32,12 @@
     pandas_dtype,
 )
 from pandas.core.dtypes.dtypes import PeriodDtype
-from pandas.core.dtypes.generic import ABCIndexClass, ABCPeriodIndex, ABCSeries
+from pandas.core.dtypes.generic import (
+    ABCIndexClass,
+    ABCPeriodIndex,
+    ABCSeries,
+    ABCTimedeltaArray,
+)
 from pandas.core.dtypes.missing import isna, notna
 
 import pandas.core.algorithms as algos
@@ -707,7 +712,9 @@ def _add_timedelta_arraylike(self, other):
         """
         if not isinstance(self.freq, Tick):
             # We cannot add timedelta-like to non-tick PeriodArray
-            raise raise_on_incompatible(self, other)
+            raise TypeError(
+                f"Cannot add or subtract timedelta64[ns] dtype from {self.dtype}"
+            )
 
         if not np.all(isna(other)):
             delta = self._check_timedeltalike_freq_compat(other)
@@ -784,7 +791,7 @@ def raise_on_incompatible(left, right):
         Exception to be raised by the caller.
     """
     # GH#24283 error message format depends on whether right is scalar
-    if isinstance(right, np.ndarray) or right is None:
+    if isinstance(right, (np.ndarray, ABCTimedeltaArray)) or right is None:
         other_freq = None
     elif isinstance(right, (ABCPeriodIndex, PeriodArray, Period, DateOffset)):
         other_freq = right.freqstr

pandas/core/arrays/timedeltas.py

@@ -4,7 +4,7 @@
 import numpy as np
 
 from pandas._libs import lib, tslibs
-from pandas._libs.tslibs import NaT, Timedelta, Timestamp, iNaT
+from pandas._libs.tslibs import NaT, Period, Timedelta, Timestamp, iNaT
 from pandas._libs.tslibs.fields import get_timedelta_field
 from pandas._libs.tslibs.timedeltas import (
     array_to_timedelta64,
@@ -404,6 +404,17 @@ def _add_offset(self, other):
             f"cannot add the type {type(other).__name__} to a {type(self).__name__}"
         )
 
+    def _add_period(self, other: Period):
+        """
+        Add a Period object.
+        """
+        # We will wrap in a PeriodArray and defer to the reversed operation
+        from .period import PeriodArray
+
+        i8vals = np.broadcast_to(other.ordinal, self.shape)
+        oth = PeriodArray(i8vals, freq=other.freq)
+        return oth + self
+
     def _add_datetime_arraylike(self, other):
         """
         Add DatetimeArray/Index or ndarray[datetime64] to TimedeltaArray.

pandas/tests/arithmetic/test_period.py

@@ -10,7 +10,7 @@
 from pandas.errors import PerformanceWarning
 
 import pandas as pd
-from pandas import Period, PeriodIndex, Series, period_range
+from pandas import Period, PeriodIndex, Series, TimedeltaIndex, Timestamp, period_range
 import pandas._testing as tm
 from pandas.core import ops
 from pandas.core.arrays import TimedeltaArray
@@ -730,13 +730,13 @@ def test_pi_add_sub_td64_array_non_tick_raises(self):
         tdi = pd.TimedeltaIndex(["-1 Day", "-1 Day", "-1 Day"])
         tdarr = tdi.values
 
-        msg = r"Input has different freq=None from PeriodArray\(freq=Q-DEC\)"
-        with pytest.raises(IncompatibleFrequency, match=msg):
+        msg = r"Cannot add or subtract timedelta64\[ns\] dtype from period\[Q-DEC\]"
+        with pytest.raises(TypeError, match=msg):
             rng + tdarr
-        with pytest.raises(IncompatibleFrequency, match=msg):
+        with pytest.raises(TypeError, match=msg):
             tdarr + rng
 
-        with pytest.raises(IncompatibleFrequency, match=msg):
+        with pytest.raises(TypeError, match=msg):
             rng - tdarr
         msg = r"cannot subtract PeriodArray from timedelta64\[ns\]"
         with pytest.raises(TypeError, match=msg):
@@ -773,6 +773,48 @@ def test_pi_add_sub_td64_array_tick(self):
         with pytest.raises(TypeError, match=msg):
             tdi - rng
 
+    @pytest.mark.parametrize("pi_freq", ["D", "W", "Q", "H"])
+    @pytest.mark.parametrize("tdi_freq", [None, "H"])
+    def test_parr_sub_td64array(self, box_with_array, tdi_freq, pi_freq):
+        box = box_with_array
+        xbox = box if box is not tm.to_array else pd.Index
+
+        tdi = TimedeltaIndex(["1 hours", "2 hours"], freq=tdi_freq)
+        dti = Timestamp("2018-03-07 17:16:40") + tdi
+        pi = dti.to_period(pi_freq)
+
+        # TODO: parametrize over box for pi?
+        td64obj = tm.box_expected(tdi, box)
+
+        if pi_freq == "H":
+            result = pi - td64obj
+            expected = (pi.to_timestamp("S") - tdi).to_period(pi_freq)
+            expected = tm.box_expected(expected, xbox)
+            tm.assert_equal(result, expected)
+
+            # Subtract from scalar
+            result = pi[0] - td64obj
+            expected = (pi[0].to_timestamp("S") - tdi).to_period(pi_freq)
+            expected = tm.box_expected(expected, box)
+            tm.assert_equal(result, expected)
+
+        elif pi_freq == "D":
+            # Tick, but non-compatible
+            msg = "Input has different freq=None from PeriodArray"
+            with pytest.raises(IncompatibleFrequency, match=msg):
+                pi - td64obj
+            with pytest.raises(IncompatibleFrequency, match=msg):
+                pi[0] - td64obj
+
+        else:
+            # With non-Tick freq, we could not add timedelta64 array regardless
+            #  of what its resolution is
+            msg = "Cannot add or subtract timedelta64"
+            with pytest.raises(TypeError, match=msg):
+                pi - td64obj
+            with pytest.raises(TypeError, match=msg):
+                pi[0] - td64obj
+
     # -----------------------------------------------------------------
     # operations with array/Index of DateOffset objects
 

pandas/tests/arithmetic/test_timedelta64.py

@@ -1081,16 +1081,9 @@ def test_td64arr_sub_periodlike(self, box_with_array, tdi_freq, pi_freq):
         with pytest.raises(TypeError, match=msg):
             tdi - pi
 
-        # FIXME: don't leave commented-out
-        # FIXME: this raises with period scalar but not with PeriodIndex?
-        # with pytest.raises(TypeError):
-        #    pi - tdi
-
         # GH#13078 subtraction of Period scalar not supported
         with pytest.raises(TypeError, match=msg):
             tdi - pi[0]
-        with pytest.raises(TypeError, match=msg):
-            pi[0] - tdi
 
     @pytest.mark.parametrize(
         "other",