gh-130472: Show PyREPL completion menus left to right

Author: pablogsal

Lib/_pyrepl/readline.py

@@ -110,7 +110,7 @@ class ReadlineAlikeReader(historical_reader.HistoricalReader, CompletingReader):
     # Class fields
     assume_immutable_completions = False
     use_brackets = False
-    sort_in_column = True
+    sort_in_column = False
 
     # Instance fields
     config: ReadlineConfig

Lib/test/test_pyrepl/test_pyrepl.py

@@ -1000,6 +1000,39 @@ class Obj:
         self.assertNotIn("banana", menu)
         self.assertNotIn("mro", menu)
 
+    def test_completion_menu_is_sorted_left_to_right(self):
+        namespace = {
+            "Py_AAA": 1,
+            "Py_BBB": 1,
+            "Py_CompileString": 1,
+            "Py_FatalError": 1,
+            "Py_Finalize": 1,
+            "Py_Initialize": 1,
+            "Py_IsInitialized": 1,
+            "Py_ZZZ": 1,
+        }
+        console = FakeConsole(code_to_events("Py_\t\t"))
+        console.width = 40
+        config = ReadlineConfig()
+        config.readline_completer = FancyCompleter(
+            namespace, use_colors=True
+        ).complete
+        reader = ReadlineAlikeReader(console=console, config=config)
+
+        with self.assertRaises(StopIteration):
+            while True:
+                reader.handle1()
+
+        self.assertEqual(
+            [stripcolor(row).rstrip() for row in reader.cmpltn_menu],
+            [
+                "Py_AAA            Py_BBB",
+                "Py_CompileString  Py_FatalError",
+                "Py_Finalize       Py_Initialize",
+                "Py_IsInitialized  Py_ZZZ",
+            ],
+        )
+
     def test_get_completions_sorts_colored_matches_by_visible_text(self):
         console = FakeConsole(iter(()))
         config = ReadlineConfig()