From fd4cafd4700dc03cb05fc2e5263c2666d785d6e3 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Mon, 7 Sep 2020 18:55:22 +0300
Subject: [PATCH] bpo-41720: Add "return NotImplemented" in
 turtle.Vec2D.__rmul__(). (GH-22092)

---
 Lib/test/test_turtle.py                        | 18 ++++++++++++++++--
 Lib/turtle.py                                  |  1 +
 .../2020-09-04-20-45-38.bpo-41720.PW9MzZ.rst   |  2 ++
 3 files changed, 19 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2020-09-04-20-45-38.bpo-41720.PW9MzZ.rst

diff --git a/Lib/test/test_turtle.py b/Lib/test/test_turtle.py
index 46ff4a3aac7..86d65075144 100644
--- a/Lib/test/test_turtle.py
+++ b/Lib/test/test_turtle.py
@@ -130,6 +130,14 @@ class VectorComparisonMixin:
             self.assertAlmostEqual(
                 i, j, msg='values at index {} do not match'.format(idx))
 
+class Multiplier:
+
+    def __mul__(self, other):
+        return f'M*{other}'
+
+    def __rmul__(self, other):
+        return f'{other}*M'
+
 
 class TestVec2D(VectorComparisonMixin, unittest.TestCase):
 
@@ -211,9 +219,15 @@ class TestVec2D(VectorComparisonMixin, unittest.TestCase):
         self.assertAlmostEqual(answer, expected)
 
         vec = Vec2D(0.5, 3)
-        answer = vec * 10
         expected = Vec2D(5, 30)
-        self.assertVectorsAlmostEqual(answer, expected)
+        self.assertVectorsAlmostEqual(vec * 10, expected)
+        self.assertVectorsAlmostEqual(10 * vec, expected)
+        self.assertVectorsAlmostEqual(vec * 10.0, expected)
+        self.assertVectorsAlmostEqual(10.0 * vec, expected)
+
+        M = Multiplier()
+        self.assertEqual(vec * M, Vec2D(f"{vec[0]}*M", f"{vec[1]}*M"))
+        self.assertEqual(M * vec, f'M*{vec}')
 
     def test_vector_negative(self):
         vec = Vec2D(10, -10)
diff --git a/Lib/turtle.py b/Lib/turtle.py
index 92d4e5dda9c..81cfcfe8a70 100644
--- a/Lib/turtle.py
+++ b/Lib/turtle.py
@@ -258,6 +258,7 @@ class Vec2D(tuple):
     def __rmul__(self, other):
         if isinstance(other, int) or isinstance(other, float):
             return Vec2D(self[0]*other, self[1]*other)
+        return NotImplemented
     def __sub__(self, other):
         return Vec2D(self[0]-other[0], self[1]-other[1])
     def __neg__(self):
diff --git a/Misc/NEWS.d/next/Library/2020-09-04-20-45-38.bpo-41720.PW9MzZ.rst b/Misc/NEWS.d/next/Library/2020-09-04-20-45-38.bpo-41720.PW9MzZ.rst
new file mode 100644
index 00000000000..5d2a5094dde
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-09-04-20-45-38.bpo-41720.PW9MzZ.rst
@@ -0,0 +1,2 @@
+Fixed :meth:`turtle.Vec2D.__rmul__` for arguments which are not int or
+float.