Add diff() and round() methods for Index and a test for each

pandas/core/indexes/base.py

@@ -6756,6 +6756,42 @@ def infer_objects(self, copy: bool = True) -> Index:
             result._references.add_index_reference(result)
         return result
 
+    def diff(self, periods: int = 1):
+        """
+        Computes the difference between consecutive values in the Index object.
+
+        If periods is greater than 1, computes the difference between values that
+        are `periods` number of positions apart.
+
+        Parameters:
+            periods (int): The number of positions between the current and previous
+            value to compute the difference with. Default is 1.
+
+        Returns:
+        Index
+            A new Index object with the computed differences.
+
+        """
+        return Index(self.to_series().diff(periods))
+
+    def round(self, decimals: int = 0):
+        """
+        Round each value in the Index to the given number of decimals.
+
+        Parameters
+        ----------
+        decimals : int, optional
+            Number of decimal places to round to. If decimals is negative,
+            it specifies the number of positions to the left of the decimal point.
+
+        Returns
+        -------
+        Index
+            A new Index with the rounded values.
+
+        """
+        return Index(self.to_series().round(decimals))
+
     # --------------------------------------------------------------------
     # Generated Arithmetic, Comparison, and Unary Methods
 

pandas/tests/indexes/test_base.py

@@ -1270,6 +1270,36 @@ def test_sortlevel_na_position(self):
         expected = Index([np.nan, 1])
         tm.assert_index_equal(result, expected)
 
+    @pytest.mark.parametrize(
+        "periods, expected",
+        [
+            (1, Index([np.nan, 10, 10, 10, 10])),
+            (2, Index([np.nan, np.nan, 20, 20, 20])),
+            (3, Index([np.nan, np.nan, np.nan, 30, 30])),
+        ],
+    )
+    def test_index_diff(self, periods, expected):
+        # GH#19708
+        idx = Index([10, 20, 30, 40, 50])
+        result = idx.diff()
+
+        tm.assert_index_equal(result, expected)
+
+    @pytest.mark.parametrize(
+        "decimals, expected",
+        [
+            (0, Index([1, 2, 3])),
+            (1, Index([1.2, 2.3, 3.5])),
+            (2, Index([1.23, 2.35, 3.46])),
+        ],
+    )
+    def test_index_round(self, decimals, expected):
+        # GH#19708
+        idx = Index([1.234, 2.345, 3.456])
+        result = idx.round()
+
+        tm.assert_index_equal(result, expected)
+
 
 class TestMixedIntIndex(Base):
     # Mostly the tests from common.py for which the results differ