BUG: Allow addition of Timedelta to Timestamp interval

doc/source/whatsnew/v1.1.0.rst

@@ -149,7 +149,7 @@ Strings
 Interval
 ^^^^^^^^
 
--
+- Fixed bug in :class:`Interval` where a :class:`Timedelta` could not be added or subtracted from a :class:`Timestamp` interval (:issue:`32023`)
 -
 
 Indexing

pandas/_libs/interval.pyx

@@ -383,14 +383,14 @@ cdef class Interval(IntervalMixin):
         return f'{start_symbol}{left}, {right}{end_symbol}'
 
     def __add__(self, y):
-        if isinstance(y, numbers.Number):
+        if isinstance(y, (numbers.Number, Timedelta)):
             return Interval(self.left + y, self.right + y, closed=self.closed)
         elif isinstance(y, Interval) and isinstance(self, numbers.Number):
             return Interval(y.left + self, y.right + self, closed=y.closed)
         return NotImplemented
 
     def __sub__(self, y):
-        if isinstance(y, numbers.Number):
+        if isinstance(y, (numbers.Number, Timedelta)):
             return Interval(self.left - y, self.right - y, closed=self.closed)
         return NotImplemented
 

pandas/tests/arithmetic/test_interval.py

@@ -271,3 +271,18 @@ def test_index_series_compat(self, op, constructor, expected_type, assert_func):
         result = op(index, other)
         expected = expected_type(self.elementwise_comparison(op, index, other))
         assert_func(result, expected)
+
+
+@pytest.mark.parametrize("method", ["__add__", "__sub__"])
+def test_timestamp_interval_add_subtract_timedelta(method):
+    # https://github.com/pandas-dev/pandas/issues/32023
+    interval = Interval(
+        Timestamp("2017-01-01 00:00:00"), Timestamp("2018-01-01 00:00:00")
+    )
+    delta = Timedelta(days=7)
+    result = getattr(interval, method)(delta)
+    left = getattr(interval.left, method)(delta)
+    right = getattr(interval.right, method)(delta)
+    expected = Interval(left, right)
+
+    assert result == expected