BUG: MultiIndex displays incorrectly with a long element (#53044)

* if branch may not be visited, so head and tail may not be correctly set

* fixed pylint possibly undefined variable

* updated changelog

* added unit test

Author: Charlie-XIAO

doc/source/whatsnew/v2.1.0.rst

@@ -376,7 +376,7 @@ I/O
 - Bug in :func:`read_hdf` not properly closing store after a ``IndexError`` is raised (:issue:`52781`)
 - Bug in :func:`read_html`, style elements were read into DataFrames (:issue:`52197`)
 - Bug in :func:`read_html`, tail texts were removed together with elements containing ``display:none`` style (:issue:`51629`)
--
+- Bug in displaying a :class:`MultiIndex` with a long element (:issue:`52960`)
 
 Period
 ^^^^^^

pandas/io/formats/printing.py

@@ -412,12 +412,14 @@ def best_len(values: list[str]) -> int:
             # max_space
             max_space = display_width - len(space2)
             value = tail[0]
-            for max_items in reversed(range(1, len(value) + 1)):
-                pprinted_seq = _pprint_seq(value, max_seq_items=max_items)
+            max_items = 1
+            for num_items in reversed(range(1, len(value) + 1)):
+                pprinted_seq = _pprint_seq(value, max_seq_items=num_items)
                 if len(pprinted_seq) < max_space:
-                    head = [_pprint_seq(x, max_seq_items=max_items) for x in head]
-                    tail = [_pprint_seq(x, max_seq_items=max_items) for x in tail]
+                    max_items = num_items
                     break
+            head = [_pprint_seq(x, max_seq_items=max_items) for x in head]
+            tail = [_pprint_seq(x, max_seq_items=max_items) for x in tail]
 
         summary = ""
         line = space2

pandas/tests/io/formats/test_printing.py

@@ -196,3 +196,14 @@ def test_enable_data_resource_formatter(self, ip):
             assert formatters[mimetype].enabled
             # smoke test that it works
             ip.instance(config=ip.config).display_formatter.format(cf)
+
+
+def test_multiindex_long_element():
+    # Non-regression test towards GH #52960
+    data = pd.MultiIndex.from_tuples([("c" * 62,)])
+
+    expected = (
+        "MultiIndex([('cccccccccccccccccccccccccccccccccccccccc"
+        "cccccccccccccccccccccc',)],\n           )"
+    )
+    assert str(data) == expected