Fix an issue with IntervalIndex.repr when null values are present (#…

…13958)

closes #13954 

This PR fixes an issue with `IntervalIndex.repr`, where there was a silent failure because of no dedicated `_clean_nulls_from_index` and the `GenericIndex._clean_nulls_from_index` wouldn't work because a type-cast to `str` isn't implemented.

Authors:
  - GALI PREM SAGAR (https://github.com/galipremsagar)

Approvers:
  - Matthew Roeschke (https://github.com/mroeschke)

URL: #13958

python/cudf/cudf/core/dtypes.py

@@ -905,9 +905,12 @@ def __init__(self, subtype, closed="right"):
     def subtype(self):
         return self.fields["left"]
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return f"interval[{self.subtype}, {self.closed}]"
 
+    def __str__(self) -> str:
+        return self.__repr__()
+
     @classmethod
     def from_arrow(cls, typ):
         return IntervalDtype(typ.subtype.to_pandas_dtype(), typ.closed)

python/cudf/cudf/core/index.py

@@ -3187,7 +3187,7 @@ def from_breaks(breaks, closed="right", name=None, copy=False, dtype=None):
         >>> import cudf
         >>> import pandas as pd
         >>> cudf.IntervalIndex.from_breaks([0, 1, 2, 3])
-        IntervalIndex([(0, 1], (1, 2], (2, 3]], dtype='interval')
+        IntervalIndex([(0, 1], (1, 2], (2, 3]], dtype='interval[int64, right]')
         """
         if copy:
             breaks = column.as_column(breaks, dtype=dtype).copy()
@@ -3211,6 +3211,9 @@ def _is_interval(self):
     def _is_boolean(self):
         return False
 
+    def _clean_nulls_from_index(self):
+        return self
+
 
 class StringIndex(GenericIndex):
     """String defined indices into another Column

python/cudf/cudf/tests/test_repr.py

@@ -1469,3 +1469,16 @@ def test_repr_struct_after_concat():
     pdf = df.to_pandas()
 
     assert repr(df) == repr(pdf)
+
+
+def test_interval_index_repr():
+    pi = pd.Index(
+        [
+            np.nan,
+            pd.Interval(2.0, 3.0, closed="right"),
+            pd.Interval(3.0, 4.0, closed="right"),
+        ]
+    )
+    gi = cudf.from_pandas(pi)
+
+    assert repr(pi) == repr(gi)