Backport PR #37288 on branch 1.1.x (Regression in offsets caused offsets to be no longer hashable)

doc/source/whatsnew/v1.1.4.rst

@@ -21,6 +21,7 @@ Fixed regressions
 - Fixed regression in :meth:`Series.astype` converting ``None`` to ``"nan"`` when casting to string (:issue:`36904`)
 - Fixed regression in :class:`RollingGroupby` causing a segmentation fault with Index of dtype object (:issue:`36727`)
 - Fixed regression in :class:`PeriodDtype` comparing both equal and unequal to its string representation (:issue:`37265`)
+- Fixed regression in certain offsets (:meth:`pd.offsets.Day() <pandas.tseries.offsets.Day>` and below) no longer being hashable (:issue:`37267`)
 
 .. ---------------------------------------------------------------------------
 

pandas/_libs/tslibs/offsets.pyx

@@ -785,6 +785,11 @@ cdef class Tick(SingleConstructorOffset):
     def is_anchored(self) -> bool:
         return False
 
+    # This is identical to BaseOffset.__hash__, but has to be redefined here
+    # for Python 3, because we've redefined __eq__.
+    def __hash__(self) -> int:
+        return hash(self._params)
+
     # --------------------------------------------------------------------
     # Comparison and Arithmetic Methods
 

pandas/tests/tseries/offsets/test_offsets.py

@@ -685,6 +685,11 @@ def test_isAnchored_deprecated(self, offset_types):
         expected = off.is_anchored()
         assert result == expected
 
+    def test_offsets_hashable(self, offset_types):
+        # GH: 37267
+        off = self._get_offset(offset_types)
+        assert hash(off) is not None
+
 
 class TestDateOffset(Base):
     def setup_method(self, method):