Add tests for Index.format

Author: topper-123

pandas/core/indexes/range.py

@@ -197,9 +197,6 @@ def _format_data(self, name=None):
         # we are formatting thru the attributes
         return None
 
-    def _format_with_header(self, header, na_rep="NaN") -> List[str]:
-        return header + [pprint_thing(x) for x in self._range]
-
     # --------------------------------------------------------------------
     _deprecation_message = (
         "RangeIndex.{} is deprecated and will be "

pandas/tests/indexes/categorical/test_category.py

@@ -478,3 +478,9 @@ def test_reindex_base(self):
     def test_map_str(self):
         # See test_map.py
         pass
+
+    def test_format_different_scalar_lengths(self):
+        # GH35439
+        idx = CategoricalIndex(["aaaaaaaaa", "b"])
+        expected = ["aaaaaaaaa", "b"]
+        assert idx.format() == expected

pandas/tests/indexes/common.py

@@ -642,6 +642,12 @@ def test_equals_op(self):
             tm.assert_numpy_array_equal(index_a == item, expected3)
             tm.assert_series_equal(series_a == item, Series(expected3))
 
+    def test_format(self):
+        # GH35439
+        idx = self.create_index()
+        expected = [str(x) for x in idx]
+        assert idx.format() == expected
+
     def test_hasnans_isnans(self, index):
         # GH 11343, added tests for hasnans / isnans
         if isinstance(index, MultiIndex):

pandas/tests/indexes/datetimes/test_datetimelike.py

@@ -20,6 +20,11 @@ def index(self, request):
     def create_index(self) -> DatetimeIndex:
         return date_range("20130101", periods=5)
 
+    def test_format(self):
+        idx = self.create_index()
+        expected = [f"{x:%Y-%m-%d}" for x in idx]
+        assert idx.format() == expected
+
     def test_shift(self):
         pass  # handled in test_ops
 

pandas/tests/indexes/test_base.py

@@ -1171,8 +1171,11 @@ def test_summary_bug(self):
         assert "~:{range}:0" in result
         assert "{other}%s" in result
 
-    def test_format(self, index):
-        self._check_method_works(Index.format, index)
+    def test_format_different_scalar_lengths(self):
+        # GH35439
+        idx = Index(["aaaaaaaaa", "b"])
+        expected = ["aaaaaaaaa", "b"]
+        assert idx.format() == expected
 
     def test_format_bug(self):
         # GH 14626

pandas/tests/indexes/test_numeric.py

@@ -21,6 +21,12 @@ def test_can_hold_identifiers(self):
         key = idx[0]
         assert idx._can_hold_identifiers_and_holds_name(key) is False
 
+    def test_format(self):
+        idx = self.create_index()
+        max_width = max(len(str(x)) for x in idx)
+        expected = [str(x).ljust(max_width) for x in idx]
+        assert idx.format() == expected
+
     def test_numeric_compat(self):
         pass  # override Base method