ENH: Support For Interval __contains__ Other Interval (pandas-dev#46613)

Author: kapiliyer

doc/source/whatsnew/v1.5.0.rst

@@ -279,6 +279,7 @@ Other enhancements
 - :class:`Series` reducers (e.g. ``min``, ``max``, ``sum``, ``mean``) will now successfully operate when the dtype is numeric and ``numeric_only=True`` is provided; previously this would raise a ``NotImplementedError`` (:issue:`47500`)
 - :meth:`RangeIndex.union` now can return a :class:`RangeIndex` instead of a :class:`Int64Index` if the resulting values are equally spaced (:issue:`47557`, :issue:`43885`)
 - :meth:`DataFrame.compare` now accepts an argument ``result_names`` to allow the user to specify the result's names of both left and right DataFrame which are being compared. This is by default ``'self'`` and ``'other'`` (:issue:`44354`)
+- :class:`Interval` now supports checking whether one interval is inside of another interval (:issue:`46613`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_150.notable_bug_fixes:

pandas/_libs/interval.pyi

@@ -81,10 +81,17 @@ class Interval(IntervalMixin, Generic[_OrderableT]):
     def __hash__(self) -> int: ...
     @overload
     def __contains__(
-        self: Interval[_OrderableTimesT], key: _OrderableTimesT
+        self: Interval[Timedelta], key: Timedelta | Interval[Timedelta]
     ) -> bool: ...
     @overload
-    def __contains__(self: Interval[_OrderableScalarT], key: int | float) -> bool: ...
+    def __contains__(
+        self: Interval[Timestamp], key: Timestamp | Interval[Timestamp]
+    ) -> bool: ...
+    @overload
+    def __contains__(
+        self: Interval[_OrderableScalarT],
+        key: _OrderableScalarT | Interval[_OrderableScalarT],
+    ) -> bool: ...
     @overload
     def __add__(
         self: Interval[_OrderableTimesT], y: Timedelta

pandas/_libs/interval.pyx

@@ -297,10 +297,12 @@ cdef class Interval(IntervalMixin):
     >>> iv
     Interval(0, 5, inclusive='right')
 
-    You can check if an element belongs to it
+    You can check if an element belongs to it, or if it contains another interval:
 
     >>> 2.5 in iv
     True
+    >>> pd.Interval(left=2, right=5, inclusive='both') in iv
+    True
 
     You can test the bounds (``inclusive='right'``, so ``0 < x <= 5``):
 
@@ -407,10 +409,12 @@ cdef class Interval(IntervalMixin):
         return hash((self.left, self.right, self.inclusive))
 
     def __contains__(self, key) -> bool:
-        if _interval_like(key):
-            raise TypeError("__contains__ not defined for two intervals")
-        return ((self.left < key if self.open_left else self.left <= key) and
-                (key < self.right if self.open_right else key <= self.right))
+        if isinstance(key, Interval):
+            return ((self.left < key.left if self.open_left and key.closed_left else self.left <= key.left) and
+                    (key.right < self.right if self.open_right and key.closed_right else key.right <= self.right))
+        elif isinstance(key, _Timestamp) or is_timedelta64_object(key) or is_float_object(key) or is_integer_object(key):
+            return ((self.left < key if self.open_left else self.left <= key) and
+                    (key < self.right if self.open_right else key <= self.right))
 
     def __richcmp__(self, other, op: int):
         if isinstance(other, Interval):

pandas/tests/scalar/interval/test_interval.py

@@ -36,10 +36,6 @@ def test_contains(self, interval):
         assert 1 in interval
         assert 0 not in interval
 
-        msg = "__contains__ not defined for two intervals"
-        with pytest.raises(TypeError, match=msg):
-            interval in interval
-
         interval_both = Interval(0, 1, "both")
         assert 0 in interval_both
         assert 1 in interval_both

pandas/tests/scalar/interval/test_ops.py

@@ -66,3 +66,58 @@ def test_overlaps_invalid_type(self, other):
         msg = f"`other` must be an Interval, got {type(other).__name__}"
         with pytest.raises(TypeError, match=msg):
             interval.overlaps(other)
+
+
+class TestContains:
+    @pytest.mark.parametrize(
+        "closed",
+        ["neither", "left", "right"],
+    )
+    def test_contains_interval(self, closed):
+        interval1 = Interval(0, 1, "both")
+        interval2 = Interval(0, 1, closed)
+        assert interval1 in interval1
+        assert interval2 in interval2
+        assert interval2 in interval1
+        assert interval1 not in interval2
+
+    def test_contains_infinite_length(self):
+        interval1 = Interval(0, 1, "both")
+        interval2 = Interval(float("-inf"), float("inf"), "neither")
+        assert interval1 in interval2
+        assert interval2 not in interval1
+
+    def test_contains_zero_length(self):
+        interval1 = Interval(0, 1, "both")
+        interval2 = Interval(-1, -1, "both")
+        interval3 = Interval(0.5, 0.5, "both")
+        assert interval2 not in interval1
+        assert interval3 in interval1
+        assert interval2 not in interval3 and interval3 not in interval2
+        assert interval1 not in interval2 and interval1 not in interval3
+
+    @pytest.mark.parametrize(
+        "type1",
+        [
+            (0, 1),
+            (Timestamp(2000, 1, 1, 0), Timestamp(2000, 1, 1, 1)),
+            (Timedelta("0h"), Timedelta("1h")),
+        ],
+    )
+    @pytest.mark.parametrize(
+        "type2",
+        [
+            (0, 1),
+            (Timestamp(2000, 1, 1, 0), Timestamp(2000, 1, 1, 1)),
+            (Timedelta("0h"), Timedelta("1h")),
+        ],
+    )
+    def test_contains_mixed_types(self, type1, type2):
+        interval1 = Interval(*type1)
+        interval2 = Interval(*type2)
+        if type1 == type2:
+            assert interval1 in interval2
+        else:
+            msg = "^'<=' not supported between instances of"
+            with pytest.raises(TypeError, match=msg):
+                interval1 in interval2