gh-152037: Raise ValueError for turtle.degrees(0) instead of ZeroDivisionError

_setDegreesPerAU divided 360 by fullcircle with no check, so the public degrees(0) raised a cryptic ZeroDivisionError. It now raises a clear ValueError. radians() passes math.tau and is unaffected. Adds a regression test and a Misc/NEWS entry.

Author: CharlesCNorton

Lib/test/test_turtle.py

@@ -368,6 +368,11 @@ def test_radians_and_degrees(self):
         self.nav.degrees()
         self.assertAlmostEqual(self.nav.heading(), 90)
 
+    def test_degrees_zero(self):
+        # degrees(0) used to raise ZeroDivisionError from 360/fullcircle.
+        with self.assertRaises(ValueError):
+            self.nav.degrees(0)
+
     def test_towards(self):
 
         coordinates = [

Lib/turtle.py

@@ -1615,6 +1615,8 @@ def _setmode(self, mode=None):
 
     def _setDegreesPerAU(self, fullcircle):
         """Helper function for degrees() and radians()"""
+        if fullcircle == 0:
+            raise ValueError("fullcircle must be a nonzero number")
         self._fullcircle = fullcircle
         self._degreesPerAU = 360/fullcircle
         if self._mode == "standard":

Misc/NEWS.d/next/Library/2026-06-23-19-41-01.gh-issue-152037.KjWrdg.rst

@@ -0,0 +1,2 @@
+Fix :exc:`ZeroDivisionError` in :func:`turtle.degrees` when *fullcircle* is
+``0``; it now raises :exc:`ValueError`.