Truncade columns list to match truncated frame for correct dict forma…

…tters lookup

pandas/io/formats/format.py

@@ -722,6 +722,7 @@ def _chk_truncate(self) -> None:
  self.truncate_h = truncate_h
  self.truncate_v = truncate_v
  self.is_truncated = bool(self.truncate_h or self.truncate_v)
+ self.columns = self.tr_frame.columns
 
  def _to_str_columns(self) -> List[List[str]]:
  """

pandas/tests/io/formats/test_format.py

@@ -689,6 +689,31 @@ def test_to_string_with_formatters(self):
  )
  assert result == result2
 
+ def test_to_string_with_truncated_formatters(self):
+ df = DataFrame(
+ {
+ "int": [1, 2, 3],
+ "float": [1.0, 2.0, 3.0],
+ "object": [(1, 2), True, False],
+ },
+ columns=["int", "float", "object"],
+ )
+
+ formatters = [
+ ("int", lambda x: f"[1] {x}"),
+ ("float", lambda x: f"[2] {x}"),
+ ("object", lambda x: f"[3] {x}"),
+ ]
+ result = df.to_string(formatters=dict(formatters), max_cols=2)
+ result2 = df.to_string(formatters=list(zip(*formatters))[1], 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"
+ )
+ assert result == result2
+
  def test_to_string_with_datetime64_monthformatter(self):
  months = [datetime(2016, 1, 1), datetime(2016, 2, 2)]
  x = DataFrame({"months": months})