From c49c7db48deaf9fae11a7f1782d65370be89c37a Mon Sep 17 00:00:00 2001
From: aouxwoux <81102668+aouxwoux@users.noreply.github.com>
Date: Fri, 10 Jul 2026 17:18:44 +0530
Subject: [PATCH 1/2] Improve parametrize error for non-sequence values

Signed-off-by: aouxwoux <81102668+aouxwoux@users.noreply.github.com>
---
 src/_pytest/mark/structures.py | 13 +++++++++++--
 testing/test_mark.py           | 20 ++++++++++++++++++++
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/src/_pytest/mark/structures.py b/src/_pytest/mark/structures.py
index 5449b17a1c6..07c202fb952 100644
--- a/src/_pytest/mark/structures.py
+++ b/src/_pytest/mark/structures.py
@@ -214,7 +214,16 @@ def _for_parametrize(
         if parameters:
             # Check all parameter sets have the correct number of values.
             for param in parameters:
-                if len(param.values) != len(argnames):
+                try:
+                    values_len = len(param.values)
+                except TypeError:
+                    fail(
+                        f'{nodeid}: in "parametrize" expected a sequence of values, '
+                        f"got {param.values!r}",
+                        pytrace=False,
+                    )
+
+                if values_len != len(argnames):
                     msg = (
                         '{nodeid}: in "parametrize" the number of names ({names_len}):\n'
                         "  {names}\n"
@@ -227,7 +236,7 @@ def _for_parametrize(
                             values=param.values,
                             names=argnames,
                             names_len=len(argnames),
-                            values_len=len(param.values),
+                            values_len=values_len,
                         ),
                         pytrace=False,
                     )
diff --git a/testing/test_mark.py b/testing/test_mark.py
index 253cda94503..78a8c88e7e4 100644
--- a/testing/test_mark.py
+++ b/testing/test_mark.py
@@ -495,6 +495,26 @@ def test_func(foo, bar):
     )
 
 
+def test_parametrized_collect_with_non_sequence_value(pytester: Pytester) -> None:
+    """Test parametrization reports non-sequence values without crashing."""
+    py_file = pytester.makepyfile(
+        """
+        import pytest
+
+        @pytest.mark.parametrize("value,", [None])
+        def test_func(value):
+            pass
+    """
+    )
+
+    result = pytester.runpytest(py_file)
+    result.stdout.fnmatch_lines(
+        [
+            '*in "parametrize" expected a sequence of values, got None',
+        ]
+    )
+
+
 def test_parametrized_with_kwargs(pytester: Pytester) -> None:
     """Test collect parametrized func with wrong number of args."""
     py_file = pytester.makepyfile(

From 01ac732aa52abe17c981a145b5d1940f90246a24 Mon Sep 17 00:00:00 2001
From: aouxwoux <81102668+aouxwoux@users.noreply.github.com>
Date: Fri, 10 Jul 2026 17:19:46 +0530
Subject: [PATCH 2/2] Add changelog for parametrize error

Signed-off-by: aouxwoux <81102668+aouxwoux@users.noreply.github.com>
---
 changelog/14619.bugfix.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog/14619.bugfix.rst

diff --git a/changelog/14619.bugfix.rst b/changelog/14619.bugfix.rst
new file mode 100644
index 00000000000..e50fc05dd5f
--- /dev/null
+++ b/changelog/14619.bugfix.rst
@@ -0,0 +1 @@
+Parametrization now reports a clear collection error when a trailing-comma argument receives a non-sequence value, instead of raising an internal ``TypeError``.