matplotlib
diff --git a/‎lib/matplotlib/legend.py‎
Lines changed: 19 additions & 0 deletions b/‎lib/matplotlib/legend.py‎
Lines changed: 19 additions & 0 deletions
diff --git a/‎lib/matplotlib/tests/test_legend.py‎
Lines changed: 68 additions & 0 deletions b/‎lib/matplotlib/tests/test_legend.py‎
Lines changed: 68 additions & 0 deletions
@@ -23,6 +23,7 @@
 
 import itertools
 import logging
+import numbers
 import time
 
 import numpy as np
@@ -535,6 +536,24 @@ def val_or_rc(val, rc_name):
                     loc = locs[0] + ' ' + locs[1]
             # check that loc is in acceptable strings
             loc = _api.check_getitem(self.codes, loc=loc)
+        elif isinstance(loc, tuple):
+            # validate the tuple represents Real coordinates
+            if len(loc) != 2 or not (all(isinstance(e, numbers.Real)
+                                         for e in loc)):
+                raise ValueError(
+                    "loc must be string, coordinate tuple or," +
+                    f" an integer 0-10, not {loc!r}")
+        elif isinstance(loc, int):
+            # validate the integer represents a string numeric value
+            if (loc < 0) or (loc > 10):
+                raise ValueError(
+                    "loc must be string, coordinate tuple or," +
+                    f" an integer 0-10, not {loc!r}")
+        else:
+            # all other cases are invalid values of loc
+            raise ValueError(
+                "loc must be string, coordinate tuple or," +
+                f" an integer 0-10, not {loc!r}")
 
         if self.isaxes and self._outside_loc:
             raise ValueError(
 
@@ -1219,3 +1219,71 @@ 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) as errorinfo:
+        ax.legend(loc=(1.1, ))
+    s = ("loc must be string, coordinate tuple or, an integer 0-10, not "
+         "(1.1,)")
+    assert s == str(errorinfo.value)
+
+    with pytest.raises(ValueError) as errorinfo:
+        ax.legend(loc=(0.481, 0.4227, 0.4523))
+    s = ("loc must be string, coordinate tuple or, an integer 0-10, not "
+         "(0.481, 0.4227, 0.4523)")
+    assert s == str(errorinfo.value)
+
+    with pytest.raises(ValueError) as errorinfo:
+        ax.legend(loc=(0.481, "go blue"))
+    s = ("loc must be string, coordinate tuple or, an integer 0-10, not "
+          "(0.481, 'go blue')")
+    assert s == str(errorinfo.value)
+
+
+def test_loc_valid_tuple():
+    fig, ax = plt.subplots()
+    ax.legend(loc=(0.481, 0.442))
+    ax.legend(loc=(1, 2))
+
+
+def test_loc_validation_string_numeric_value():
+    fig, ax = plt.subplots()
+    ax.legend(loc=0)
+    ax.legend(loc=1)
+    ax.legend(loc=5)
+    ax.legend(loc=10)
+    with pytest.raises(ValueError) as errorinfo:
+        ax.legend(loc=11)
+    s = "loc must be string, coordinate tuple or, an integer 0-10, not 11"
+    assert s == str(errorinfo.value)
+
+    with pytest.raises(ValueError) as errorinfo:
+        ax.legend(loc=-1)
+    s = "loc must be string, coordinate tuple or, an integer 0-10, not -1"
+    assert s == str(errorinfo.value)
+
+
+def test_loc_validation_string_value():
+    fig, ax = plt.subplots()
+    ax.legend(loc='best')
+    ax.legend(loc='upper right')
+    ax.legend(loc='best')
+    ax.legend(loc='upper right')
+    ax.legend(loc='upper left')
+    ax.legend(loc='lower left')
+    ax.legend(loc='lower right')
+    ax.legend(loc='right')
+    ax.legend(loc='center left')
+    ax.legend(loc='center right')
+    ax.legend(loc='lower center')
+    ax.legend(loc='upper center')
+    with pytest.raises(ValueError) as errorinfo:
+        ax.legend(loc='wrong')
+    s = ("'wrong' is not a valid value for loc; supported values are 'best',"
+         " 'upper right', 'upper left', 'lower left', 'lower right', 'right',"
+         " 'center left', 'center right', 'lower center', 'upper center', 'center'")
+    assert s == str(errorinfo.value)