gh-95144: Improve error message of ... in None

Author: zware

Lib/test/test_contains.py

@@ -24,8 +24,11 @@ def test_common_tests(self):
  self.assertNotIn(0, b)
  self.assertIn(1, c)
  self.assertNotIn(0, c)
- self.assertRaises(TypeError, lambda: 1 in a)
- self.assertRaises(TypeError, lambda: 1 not in a)
+ msg = "argument of type 'base_set' is not a container or iterable"
+ with self.assertRaisesRegex(TypeError, msg):
+ 1 in a
+ with self.assertRaisesRegex(TypeError, msg):
+ 1 not in a
 
  # test char in string
  self.assertIn('c', 'abc')

Lib/test/test_sqlite3/test_dbapi.py

@@ -1434,7 +1434,7 @@ def test_blob_sequence_not_supported(self):
  self.blob + self.blob
  with self.assertRaisesRegex(TypeError, "unsupported operand"):
  self.blob * 5
- with self.assertRaisesRegex(TypeError, "is not iterable"):
+ with self.assertRaisesRegex(TypeError, "is not.+iterable"):
  b"a" in self.blob
 
  def test_blob_context_manager(self):

Misc/NEWS.d/next/Core and Builtins/2022-07-22-15-56-35.gh-issue-95144.FZYWX-.rst

@@ -0,0 +1,2 @@
+Improve the error message from ``a in b`` when ``b`` is not a container
+to mention the term :term:`container`.

Objects/abstract.c

@@ -2173,7 +2173,7 @@ PySequence_Fast(PyObject *v, const char *m)
  PY_ITERSEARCH_COUNT: -1 if error, else # of times obj appears in seq.
  PY_ITERSEARCH_INDEX: 0-based index of first occurrence of obj in seq;
  set ValueError and return -1 if none found; also return -1 on error.
- Py_ITERSEARCH_CONTAINS: return 1 if obj in seq, else 0; -1 on error.
+ PY_ITERSEARCH_CONTAINS: return 1 if obj in seq, else 0; -1 on error.
 */
 Py_ssize_t
 _PySequence_IterSearch(PyObject *seq, PyObject *obj, int operation)
@@ -2190,7 +2190,15 @@ _PySequence_IterSearch(PyObject *seq, PyObject *obj, int operation)
  it = PyObject_GetIter(seq);
  if (it == NULL) {
  if (PyErr_ExceptionMatches(PyExc_TypeError)) {
- type_error("argument of type '%.200s' is not iterable", seq);
+ if (operation == PY_ITERSEARCH_CONTAINS) {
+ type_error(
+ "argument of type '%.200s' is not a container or iterable",
+ seq
+ );
+ }
+ else {
+ type_error("argument of type '%.200s' is not iterable", seq);
+ }
  }
  return -1;
  }