FIX printing index with display.max_seq_items=None (GH10182)

Author: jorisvandenbossche

doc/source/whatsnew/v0.17.0.txt

@@ -61,7 +61,7 @@ Bug Fixes
 ~~~~~~~~~
 
 - Bug in ``Categorical`` repr with ``display.width`` of ``None`` in Python 3 (:issue:`10087`)
-
+- Bug in Index repr when using the ``max_seq_items=None`` setting (:issue:`10182`).
 
 - Bug where Panel.from_dict does not set dtype when specified (:issue:`10058`)
 - Bug in ``Timestamp``'s' ``microsecond``, ``quarter``, ``dayofyear``, ``week`` and ``daysinmonth`` properties return ``np.int`` type, not built-in ``int``. (:issue:`10050`)
@@ -74,5 +74,3 @@ Bug Fixes
 - Bug in ``DatetimeIndex`` and ``TimedeltaIndex`` names are lost after timedelta arithmetics ( :issue:`9926`)
 
 - Bug in `Series.plot(label="LABEL")` not correctly setting the label (:issue:`10119`)
-
-

pandas/core/index.py

@@ -443,7 +443,7 @@ def _format_data(self):
 
         n = len(self)
         sep = ','
-        max_seq_items = get_option('display.max_seq_items')
+        max_seq_items = get_option('display.max_seq_items') or n
         formatter = self._formatter_func
 
         # do we want to justify (only do so for non-objects)

pandas/tests/test_index.py

@@ -133,6 +133,14 @@ def test_str(self):
         self.assertTrue("'foo'" in str(idx))
         self.assertTrue(idx.__class__.__name__ in str(idx))
 
+    def test_repr_max_seq_item_setting(self):
+        # GH10182
+        idx = self.create_index()
+        idx = idx.repeat(50)
+        with pd.option_context("display.max_seq_items", None):
+            repr(idx)
+            self.assertFalse('...' in str(idx))
+
     def test_wrong_number_names(self):
         def testit(ind):
             ind.names = ["apple", "banana", "carrot"]