Prompt fallback when __str__ raises

Author: edvilme

Lib/_pyrepl/simple_interact.py

@@ -134,9 +134,14 @@ def maybe_run_command(statement: str) -> bool:
                 sys.stdout.flush()
             except Exception:
                 pass
-
-            ps1 = str(getattr(sys, "ps1", ">>> "))
-            ps2 = str(getattr(sys, "ps2", "... "))
+            try:
+                ps1 = str(getattr(sys, "ps1", ">>> "))
+            except Exception:
+                ps1 = ">>> "
+            try:
+                ps2 = str(getattr(sys, "ps2", "... "))
+            except Exception:
+                ps2 = "... "
             try:
                 statement = multiline_input(more_lines, ps1, ps2)
             except EOFError:

Lib/test/test_pyrepl/test_interact.py

@@ -37,6 +37,22 @@ def __str__(self):
 
         multiline_input.assert_called_once_with(ANY, "primary", "secondary")
 
+    def test_ps1_str_error_uses_default_prompt(self):
+        class Prompt:
+            def __str__(self):
+                return 1 / 0
+
+        with (
+            patch.object(sys, "ps1", Prompt(), create=True),
+            patch("_pyrepl.readline._setup"),
+            patch(
+                "_pyrepl.simple_interact.multiline_input", side_effect=EOFError
+            ) as multiline_input,
+        ):
+            run_multiline_interactive_console(InteractiveColoredConsole())
+
+        multiline_input.assert_called_once_with(ANY, ">>> ", ANY)
+
     def test_multiple_statements(self):
         namespace = {}
         code = dedent("""\