Truncate columns list to match tr_frame for correct dict formatters lookup

doc/source/whatsnew/v1.2.0.rst

@@ -750,6 +750,7 @@ I/O
 - :meth:`DataFrame.to_csv` was re-opening file-like handles that also implement ``os.PathLike`` (:issue:`38125`)
 - Bug in the conversion of a sliced ``pyarrow.Table`` with missing values to a DataFrame (:issue:`38525`)
 - Bug in :func:`read_sql_table` raising a ``sqlalchemy.exc.OperationalError`` when column names contained a percentage sign (:issue:`37517`)
+- :class:`DataFrameFormatter` was using the full list of columns when computing formatters for truncated displays (:issue:`35907`)
 
 Period
 ^^^^^^

pandas/io/formats/format.py

@@ -840,7 +840,7 @@ def _get_formatter(self, i: Union[str, int]) -> Optional[Callable]:
  return None
  else:
  if is_integer(i) and i not in self.columns:
- i = self.columns[i]
+ i = self.tr_frame.columns[i]
  return self.formatters.get(i, None)
 
  def _get_formatted_column_labels(self, frame: DataFrame) -> List[List[str]]:

pandas/tests/io/formats/test_to_string.py

@@ -167,6 +167,35 @@ def test_to_string_with_formatters():
  assert result == result2
 
 
+@pytest.mark.parametrize(
+ "formatters",
+ [
+ {
+ "int": lambda x: f"[1] {x}",
+ "float": lambda x: f"[2] {x}",
+ "object": lambda x: f"[3] {x}",
+ },
+ [lambda x: f"[1] {x}", lambda x: f"[2] {x}", lambda x: f"[3] {x}"],
+ ],
+)
+def test_to_string_with_truncated_formatters(formatters):
+ df = DataFrame(
+ {
+ "int": [1, 2, 3],
+ "float": [1.0, 2.0, 3.0],
+ "object": [(1, 2), True, False],
+ },
+ columns=["int", "float", "object"],
+ )
+ result = df.to_string(formatters=formatters, max_cols=2)
+ assert result == (
+ " int ... object\n"
+ "0 [1] 1 ... [3] (1, 2)\n"
+ "1 [1] 2 ... [3] True\n"
+ "2 [1] 3 ... [3] False"
+ )
+
+
 def test_to_string_with_datetime64_monthformatter():
  months = [datetime(2016, 1, 1), datetime(2016, 2, 2)]
  x = DataFrame({"months": months})