From c7f2f42145572e8e708fd2f01ecf4679e6534c54 Mon Sep 17 00:00:00 2001
From: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
Date: Tue, 22 Jun 2021 12:24:42 +0200
Subject: [PATCH] Backport PR #20480: Fix str of empty polygon.

---
 lib/matplotlib/patches.py            | 7 +++++--
 lib/matplotlib/tests/test_patches.py | 3 +++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/matplotlib/patches.py b/lib/matplotlib/patches.py
index a5bb2019db56..07ee830be31d 100644
--- a/lib/matplotlib/patches.py
+++ b/lib/matplotlib/patches.py
@@ -1048,8 +1048,11 @@ class Polygon(Patch):
     """A general polygon patch."""
 
     def __str__(self):
-        s = "Polygon%d((%g, %g) ...)"
-        return s % (len(self._path.vertices), *tuple(self._path.vertices[0]))
+        if len(self._path.vertices):
+            s = "Polygon%d((%g, %g) ...)"
+            return s % (len(self._path.vertices), *self._path.vertices[0])
+        else:
+            return "Polygon0()"
 
     @docstring.dedent_interpd
     def __init__(self, xy, closed=True, **kwargs):
diff --git a/lib/matplotlib/tests/test_patches.py b/lib/matplotlib/tests/test_patches.py
index 2a908098364e..4eacbac89126 100644
--- a/lib/matplotlib/tests/test_patches.py
+++ b/lib/matplotlib/tests/test_patches.py
@@ -347,6 +347,9 @@ def test_patch_str():
     p = mpatches.PathPatch(path)
     assert str(p) == "PathPatch3((1, 2) ...)"
 
+    p = mpatches.Polygon(np.empty((0, 2)))
+    assert str(p) == "Polygon0()"
+
     data = [[1, 2], [2, 2], [1, 2]]
     p = mpatches.Polygon(data)
     assert str(p) == "Polygon3((1, 2) ...)"