gh-130821: Add type information to wrong type error messages

Lib/test/test_coroutines.py

@@ -1008,7 +1008,7 @@ async def foo():
  return (await Awaitable())
 
  with self.assertRaisesRegex(
- TypeError, "__await__.*returned non-iterator of type"):
+ TypeError, "__await__.*must return an iterator, not"):
 
  run_async(foo())
 
@@ -1106,7 +1106,7 @@ async def foo():
  return await Awaitable()
 
  with self.assertRaisesRegex(
- TypeError, r"__await__\(\) returned a coroutine"):
+ TypeError, r"__await__\(\) must return an iterator, not coroutine"):
  run_async(foo())
 
  c.close()
@@ -1120,7 +1120,7 @@ async def foo():
  return await Awaitable()
 
  with self.assertRaisesRegex(
- TypeError, "__await__.*returned non-iterator of type"):
+ TypeError, "__await__.*must return an iterator, not"):
 
  run_async(foo())
 
@@ -2490,7 +2490,7 @@ async def foo():
  return (await future)
 
  with self.assertRaisesRegex(
- TypeError, "__await__.*returned non-iterator of type 'int'"):
+ TypeError, "__await__.*must return an iterator, not int"):
  self.assertEqual(foo().send(None), 1)
 
 

Lib/test/test_type_annotations.py

@@ -309,7 +309,7 @@ def check_annotations(self, f):
  print(f.__annotations__)
 
  f.__annotate__ = lambda x: 42
- with self.assertRaisesRegex(TypeError, r"__annotate__ returned non-dict of type 'int'"):
+ with self.assertRaisesRegex(TypeError, r"__annotate__\(\) must return a dict, not int"):
  print(f.__annotations__)
 
  f.__annotate__ = lambda x:{"x": x}

Misc/NEWS.d/next/Core_and_Builtins/2025-04-28-18-59-11.gh-issue-130821.B11LU1.rst

@@ -0,0 +1,2 @@
+Enhance wrong type error messages and make them more consistent. Patch by
+Semyon Moroz.

Objects/abstract.c

@@ -132,8 +132,9 @@ PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)
  return defaultvalue;
  }
  if (!PyLong_Check(result)){
- PyErr_Format(PyExc_TypeError, "__length_hint__ must be an integer, not %.100s",
- Py_TYPE(result)->tp_name);
+ PyErr_Format(PyExc_TypeError,
+ "%T.__length_hint__() must return an int, not %T",
+ o, result);
  Py_DECREF(result);
  return -1;
  }
@@ -143,7 +144,8 @@ PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)
  return -1;
  }
  if (res < 0){
- PyErr_Format(PyExc_ValueError, "__length_hint__() should return >= 0");
+ PyErr_Format(PyExc_ValueError,
+ "%T.__length_hint__() must return a non-negative int", o);
  return -1;
  }
  return res;
@@ -887,8 +889,8 @@ PyObject_Format(PyObject *obj, PyObject *format_spec)
 
  if (result && !PyUnicode_Check(result)){
  PyErr_Format(PyExc_TypeError,
- "__format__ must return a str, not %.200s",
-Py_TYPE(result)->tp_name);
+ "%T.__format__() must return a str, not %T",
+obj, result);
  Py_SETREF(result, NULL);
  goto done;
  }
@@ -1421,17 +1423,17 @@ _PyNumber_Index(PyObject *item)
 
  if (!PyLong_Check(result)){
  PyErr_Format(PyExc_TypeError,
- "__index__ returned non-int (type %.200s)",
-Py_TYPE(result)->tp_name);
+ "%T.__index__() must return an int, not %T",
+item, result);
  Py_DECREF(result);
  return NULL;
  }
  /* Issue #17576: warn if 'result' not of exact type int. */
  if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
- "__index__ returned non-int (type %.200s). "
+ "%T.__index__() must return an int, not %T. "
  "The ability to return an instance of a strict subclass of int "
  "is deprecated, and may be removed in a future version of Python.",
-Py_TYPE(result)->tp_name)){
+item, result)){
  Py_DECREF(result);
  return NULL;
  }
@@ -1531,17 +1533,17 @@ PyNumber_Long(PyObject *o)
 
  if (!PyLong_Check(result)){
  PyErr_Format(PyExc_TypeError,
- "__int__ returned non-int (type %.200s)",
-Py_TYPE(result)->tp_name);
+ "%T.__int__() must return an int, not %T",
+o, result);
  Py_DECREF(result);
  return NULL;
  }
  /* Issue #17576: warn if 'result' not of exact type int. */
  if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
- "__int__ returned non-int (type %.200s). "
+ "%T.__int__() must return an int, not %T. "
  "The ability to return an instance of a strict subclass of int "
  "is deprecated, and may be removed in a future version of Python.",
-Py_TYPE(result)->tp_name)){
+o, result)){
  Py_DECREF(result);
  return NULL;
  }
@@ -1609,17 +1611,16 @@ PyNumber_Float(PyObject *o)
 
  if (!PyFloat_Check(res)){
  PyErr_Format(PyExc_TypeError,
- "%.50s.__float__ returned non-float (type %.50s)",
- Py_TYPE(o)->tp_name, Py_TYPE(res)->tp_name);
+ "%T.__float__() must return a float, not %T", o, res);
  Py_DECREF(res);
  return NULL;
  }
  /* Issue #26983: warn if 'res' not of exact type float. */
  if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
- "%.50s.__float__ returned non-float (type %.50s). "
+ "%T.__float__() must return a float, not %T. "
  "The ability to return an instance of a strict subclass of float "
  "is deprecated, and may be removed in a future version of Python.",
-Py_TYPE(o)->tp_name, Py_TYPE(res)->tp_name)){
+o, res)){
  Py_DECREF(res);
  return NULL;
  }
@@ -2435,10 +2436,8 @@ method_output_as_list(PyObject *o, PyObject *meth)
  PyThreadState *tstate = _PyThreadState_GET();
  if (_PyErr_ExceptionMatches(tstate, PyExc_TypeError)){
  _PyErr_Format(tstate, PyExc_TypeError,
- "%.200s.%U() returned a non-iterable (type %.200s)",
- Py_TYPE(o)->tp_name,
- meth,
- Py_TYPE(meth_output)->tp_name);
+ "%T.%U() must return an iterable, not %T",
+ o, meth, meth_output);
  }
  Py_DECREF(meth_output);
  return NULL;
@@ -2818,9 +2817,8 @@ PyObject_GetIter(PyObject *o)
  PyObject *res = (*f)(o);
  if (res != NULL && !PyIter_Check(res)){
  PyErr_Format(PyExc_TypeError,
- "iter() returned non-iterator "
- "of type '%.100s'",
- Py_TYPE(res)->tp_name);
+ "%T.__iter__() must return an iterator, not %T",
+ o, res);
  Py_SETREF(res, NULL);
  }
  return res;
@@ -2839,8 +2837,8 @@ PyObject_GetAIter(PyObject *o){
  PyObject *it = (*f)(o);
  if (it != NULL && !PyAIter_Check(it)){
  PyErr_Format(PyExc_TypeError,
- "aiter() returned not an async iterator of type '%.100s'",
-Py_TYPE(it)->tp_name);
+ "%T.__aiter__() must return an async iterator, not %T",
+o, it);
  Py_SETREF(it, NULL);
  }
  return it;

Objects/bytesobject.c

@@ -566,8 +566,8 @@ format_obj(PyObject *v, const char **pbuf, Py_ssize_t *plen)
  return NULL;
  if (!PyBytes_Check(result)){
  PyErr_Format(PyExc_TypeError,
- "__bytes__ returned non-bytes (type %.200s)",
-Py_TYPE(result)->tp_name);
+ "%T.__bytes__() must return a bytes, not %T",
+v, result);
  Py_DECREF(result);
  return NULL;
  }
@@ -2793,8 +2793,8 @@ bytes_new_impl(PyTypeObject *type, PyObject *x, const char *encoding,
  return NULL;
  if (!PyBytes_Check(bytes)){
  PyErr_Format(PyExc_TypeError,
-"__bytes__ returned non-bytes (type %.200s)",
-Py_TYPE(bytes)->tp_name);
+ "%T.__bytes__() must return a bytes, not %T",
+ x, bytes);
  Py_DECREF(bytes);
  return NULL;
  }

Objects/complexobject.c

@@ -515,17 +515,17 @@ try_complex_special_method(PyObject *op)
  }
  if (!PyComplex_Check(res)){
  PyErr_Format(PyExc_TypeError,
- "__complex__ returned non-complex (type %.200s)",
-Py_TYPE(res)->tp_name);
+ "%T.__complex__() must return a complex, not %T",
+op, res);
  Py_DECREF(res);
  return NULL;
  }
  /* Issue #29894: warn if 'res' not of exact type complex. */
  if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
- "__complex__ returned non-complex (type %.200s). "
+ "%T.__complex__() must return a complex, not %T. "
  "The ability to return an instance of a strict subclass of complex "
  "is deprecated, and may be removed in a future version of Python.",
-Py_TYPE(res)->tp_name)){
+op, res)){
  Py_DECREF(res);
  return NULL;
  }

Objects/fileobject.c

@@ -68,9 +68,9 @@ PyFile_GetLine(PyObject *f, int n)
  }
  if (result != NULL && !PyBytes_Check(result) &&
  !PyUnicode_Check(result)){
+ PyErr_Format(PyExc_TypeError,
+ "%T.readline() must return a str, not %T", f, result);
  Py_SETREF(result, NULL);
- PyErr_SetString(PyExc_TypeError,
- "object.readline() returned non-string");
  }
 
  if (n < 0 && result != NULL && PyBytes_Check(result)){
@@ -193,8 +193,8 @@ PyObject_AsFileDescriptor(PyObject *o)
  Py_DECREF(fno);
  }
  else{
-PyErr_SetString(PyExc_TypeError,
- "fileno() returned a non-integer");
+PyErr_Format(PyExc_TypeError,
+"%T.fileno() must return an int, not %T", o, fno);
  Py_DECREF(fno);
  return -1;
  }

Objects/floatobject.c

@@ -288,16 +288,16 @@ PyFloat_AsDouble(PyObject *op)
  if (!PyFloat_CheckExact(res)){
  if (!PyFloat_Check(res)){
  PyErr_Format(PyExc_TypeError,
- "%.50s.__float__ returned non-float (type %.50s)",
-Py_TYPE(op)->tp_name, Py_TYPE(res)->tp_name);
+ "%T.__float__() must return a float, not %T",
+op, res);
  Py_DECREF(res);
  return -1;
  }
  if (PyErr_WarnFormat(PyExc_DeprecationWarning, 1,
- "%.50s.__float__ returned non-float (type %.50s). "
+ "%T.__float__() must return a float, not %T. "
  "The ability to return an instance of a strict subclass of float "
  "is deprecated, and may be removed in a future version of Python.",
-Py_TYPE(op)->tp_name, Py_TYPE(res)->tp_name)){
+op, res)){
  Py_DECREF(res);
  return -1;
  }

Objects/funcobject.c

@@ -560,8 +560,9 @@ func_get_annotation_dict(PyFunctionObject *op)
  return NULL;
  }
  if (!PyDict_Check(ann_dict)){
- PyErr_Format(PyExc_TypeError, "__annotate__ returned non-dict of type '%.100s'",
- Py_TYPE(ann_dict)->tp_name);
+ PyErr_Format(PyExc_TypeError,
+ "__annotate__() must return a dict, not %T",
+ ann_dict);
  Py_DECREF(ann_dict);
  return NULL;
  }

Objects/genobject.c

@@ -1092,14 +1092,14 @@ _PyCoro_GetAwaitableIter(PyObject *o)
  if (PyCoro_CheckExact(res) || gen_is_coroutine(res)){
  /* __await__ must return an *iterator*, not
  a coroutine or another awaitable (see PEP 492) */
- PyErr_SetString(PyExc_TypeError,
- "__await__() returned a coroutine");
+ PyErr_Format(PyExc_TypeError,
+ "%T.__await__() must return an iterator, "
+ "not coroutine", o);
  Py_CLEAR(res);
  } else if (!PyIter_Check(res)){
  PyErr_Format(PyExc_TypeError,
- "__await__() returned non-iterator "
- "of type '%.100s'",
- Py_TYPE(res)->tp_name);
+ "%T.__await__() must return an iterator, "
+ "not %T", o, res);
  Py_CLEAR(res);
  }
  }

Objects/iterobject.c

@@ -357,8 +357,9 @@ anextawaitable_getiter(anextawaitableobject *obj)
  }
  Py_SETREF(awaitable, new_awaitable);
  if (!PyIter_Check(awaitable)){
- PyErr_SetString(PyExc_TypeError,
- "__await__ returned a non-iterable");
+ PyErr_Format(PyExc_TypeError,
+ "%T.__await__() must return an iterable, not %T",
+ obj, awaitable);
  Py_DECREF(awaitable);
  return NULL;
  }

Objects/moduleobject.c

@@ -1329,8 +1329,9 @@ module_get_annotations(PyObject *self, void *Py_UNUSED(ignored))
  return NULL;
  }
  if (!PyDict_Check(annotations)){
- PyErr_Format(PyExc_TypeError, "__annotate__ returned non-dict of type '%.100s'",
- Py_TYPE(annotations)->tp_name);
+ PyErr_Format(PyExc_TypeError,
+ "__annotate__() must return a dict, not %T",
+ annotations);
  Py_DECREF(annotate);
  Py_DECREF(annotations);
  Py_DECREF(dict);

Objects/object.c

@@ -784,8 +784,7 @@ PyObject_Repr(PyObject *v)
  }
  if (!PyUnicode_Check(res)){
  _PyErr_Format(tstate, PyExc_TypeError,
- "__repr__ returned non-string (type %.200s)",
- Py_TYPE(res)->tp_name);
+ "%T.__repr__() must return a str, not %T", v, res);
  Py_DECREF(res);
  return NULL;
  }
@@ -827,8 +826,7 @@ PyObject_Str(PyObject *v)
  }
  if (!PyUnicode_Check(res)){
  _PyErr_Format(tstate, PyExc_TypeError,
- "__str__ returned non-string (type %.200s)",
- Py_TYPE(res)->tp_name);
+ "%T.__str__() must return a str, not %T", v, res);
  Py_DECREF(res);
  return NULL;
  }
@@ -883,8 +881,8 @@ PyObject_Bytes(PyObject *v)
  return NULL;
  if (!PyBytes_Check(result)){
  PyErr_Format(PyExc_TypeError,
- "__bytes__ returned non-bytes (type %.200s)",
-Py_TYPE(result)->tp_name);
+ "%T.__bytes__() must return a bytes, not %T",
+v, result);
  Py_DECREF(result);
  return NULL;
  }