fixed bug where pd.NA was being cast to NaN during formatting

pandas/io/formats/format.py

@@ -15,6 +15,7 @@
 from decimal import Decimal
 from functools import partial
 from io import StringIO
+from itertools import chain
 import math
 import re
 from shutil import get_terminal_size
@@ -696,9 +697,10 @@ def _truncate_vertically(self) -> None:
         assert self.max_rows_fitted is not None
         row_num = self.max_rows_fitted // 2
         if row_num >= 1:
-            head = self.tr_frame.iloc[:row_num, :]
-            tail = self.tr_frame.iloc[-row_num:, :]
-            self.tr_frame = concat((head, tail))
+            _len = len(self.tr_frame)
+            self.tr_frame = self.tr_frame.iloc[
+                chain(range(row_num), range(_len - row_num, _len))
+            ]
         else:
             row_num = cast(int, self.max_rows)
             self.tr_frame = self.tr_frame.iloc[:row_num, :]

pandas/tests/io/formats/test_format.py

@@ -171,6 +171,15 @@ def test_repr_truncation(self):
         with option_context("display.max_colwidth", max_len + 2):
             assert "..." not in repr(df)
 
+    def test_repr_truncation_preserves_na(self):
+        # https://github.com/pandas-dev/pandas/issues/55630
+        with option_context("display.max_rows", 10):
+            df = DataFrame({"A": [pd.NA for _ in range(100)]})
+
+            r = repr(df)
+            for row in r.split("\n")[1:-2]:
+                assert row.endswith(("<NA>", "..."))
+
     def test_max_colwidth_negative_int_raises(self):
         # Deprecation enforced from:
         # https://github.com/pandas-dev/pandas/issues/31532