BUG: Fix Index.__repr__ when display.max_seq_items = 1 (#38443)

Author: skvrahul

doc/source/whatsnew/v1.3.0.rst

@@ -250,6 +250,7 @@ MultiIndex
 I/O
 ^^^
 
+- Bug in :meth:`Index.__repr__` when ``display.max_seq_items=1`` (:issue:`38415`)
 - Bug in :func:`read_csv` interpreting ``NA`` value as comment, when ``NA`` does contain the comment string fixed for ``engine="python"`` (:issue:`34002`)
 - Bug in :func:`read_csv` raising ``IndexError`` with multiple header columns and ``index_col`` specified when file has no data rows (:issue:`38292`)
 - Bug in :func:`read_csv` not accepting ``usecols`` with different length than ``names`` for ``engine="python"`` (:issue:`16469`)

pandas/io/formats/printing.py

@@ -382,7 +382,11 @@ def best_len(values: List[str]) -> int:
  summary = f"[{first}, {last}]{close}"
  else:
 
- if n > max_seq_items:
+ if max_seq_items == 1:
+ # If max_seq_items=1 show only last element
+ head = []
+ tail = [formatter(x) for x in obj[-1:]]
+ elif n > max_seq_items:
  n = min(max_seq_items // 2, 10)
  head = [formatter(x) for x in obj[:n]]
  tail = [formatter(x) for x in obj[-n:]]

pandas/tests/groupby/test_groupby.py

@@ -2058,6 +2058,7 @@ def test_groupby_list_level():
  [
  (5, "{0: [0], 1: [1], 2: [2], 3: [3], 4: [4]}"),
  (4, "{0: [0], 1: [1], 2: [2], 3: [3], ...}"),
+ (1, "{0: [0], ...}"),
  ],
 )
 def test_groups_repr_truncates(max_seq_items, expected):

pandas/tests/indexes/multi/test_formats.py

@@ -89,6 +89,20 @@ def test_unicode_repr_issues(self):
  # NumPy bug
  # repr(index.get_level_values(1))
 
+ def test_repr_max_seq_items_equal_to_n(self, idx):
+ # display.max_seq_items == n
+ with pd.option_context("display.max_seq_items", 6):
+ result = idx.__repr__()
+ expected = """\
+MultiIndex([('foo', 'one'),
+ ('foo', 'two'),
+ ('bar', 'one'),
+ ('baz', 'two'),
+ ('qux', 'one'),
+ ('qux', 'two')],
+ names=['first', 'second'])"""
+ assert result == expected
+
  def test_repr(self, idx):
  result = idx[:1].__repr__()
  expected = """\
@@ -118,6 +132,15 @@ def test_repr(self, idx):
  names=['first', 'second'], length=6)"""
  assert result == expected
 
+ # display.max_seq_items == 1
+ with pd.option_context("display.max_seq_items", 1):
+ result = idx.__repr__()
+ expected = """\
+MultiIndex([...
+ ('qux', 'two')],
+ names=['first', ...], length=6)"""
+ assert result == expected
+
  def test_rjust(self, narrow_multi_index):
  mi = narrow_multi_index
  result = mi[:1].__repr__()

pandas/tests/io/formats/test_format.py

@@ -297,6 +297,9 @@ def test_repr_obeys_max_seq_limit(self):
  with option_context("display.max_seq_items", 5):
  assert len(printing.pprint_thing(list(range(1000)))) < 100
 
+ with option_context("display.max_seq_items", 1):
+ assert len(printing.pprint_thing(list(range(1000)))) < 9
+
  def test_repr_set(self):
  assert printing.pprint_thing({1}) == "{1}"