From 0b7fcba17274d73464425d8fc80ec339959c0c63 Mon Sep 17 00:00:00 2001
From: John Paul Jepko <jpjepko@umich.edu>
Date: Tue, 6 Dec 2022 16:59:30 -0500
Subject: [PATCH] #24605 add check to validate loc tuples

---
 lib/matplotlib/legend.py            |  9 +++++++++
 lib/matplotlib/tests/test_legend.py | 24 ++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/lib/matplotlib/legend.py b/lib/matplotlib/legend.py
index d0590824ad84..a64d806ae6e0 100644
--- a/lib/matplotlib/legend.py
+++ b/lib/matplotlib/legend.py
@@ -23,6 +23,7 @@
 
 import itertools
 import logging
+import numbers
 import time
 
 import numpy as np
@@ -472,6 +473,14 @@ def val_or_rc(val, rc_name):
                 loc = 'upper right'
         if isinstance(loc, str):
             loc = _api.check_getitem(self.codes, loc=loc)
+        elif isinstance(loc, tuple):
+            if len(loc) != 2 or not (all(isinstance(e, numbers.Real)
+                                         for e in loc)):
+                raise ValueError(
+                    f"loc must be string or pair of numbers, not {loc!r}")
+        else:
+            raise ValueError(
+                f"loc must be string or pair of numbers, not {loc!r}")
         if not self.isaxes and loc == 0:
             raise ValueError(
                 "Automatic legend placement (loc='best') not implemented for "
diff --git a/lib/matplotlib/tests/test_legend.py b/lib/matplotlib/tests/test_legend.py
index 6660b91ecdd9..4fd34e4321a8 100644
--- a/lib/matplotlib/tests/test_legend.py
+++ b/lib/matplotlib/tests/test_legend.py
@@ -1090,3 +1090,27 @@ def test_ncol_ncols(fig_test, fig_ref):
     ncols = 3
     fig_test.legend(strings, ncol=ncols)
     fig_ref.legend(strings, ncols=ncols)
+
+
+def test_loc_invalid_tuple_exception():
+    # check that exception is raised if the loc arg
+    # of legend is not a 2-tuple of numbers
+    fig, ax = plt.subplots()
+    with pytest.raises(ValueError,
+                       match="loc must be string or pair of numbers, not "
+                             "\\(1.1\\,\\)"):   # regex escape special chars
+        ax.legend(loc=(1.1, ))
+    with pytest.raises(ValueError,
+                       match="loc must be string or pair of numbers, not "
+                             "\\(0.481\\, 0.4227\\, 0.4523\\)"):
+        ax.legend(loc=(0.481, 0.4227, 0.4523))
+    with pytest.raises(ValueError,
+                       match="loc must be string or pair of numbers, not "
+                             "\\(0.481\\, \\'go blue\\'\\)"):
+        ax.legend(loc=(0.481, "go blue"))
+
+
+def test_loc_valid_tuple():
+    fig, ax = plt.subplots()
+    ax.legend(loc=(0.481, 0.442))
+    ax.legend(loc=(1, 2))