matplotlib
diff --git a/‎doc/api/next_api_changes/deprecations/26444-ES.rst
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+5Lines changed: 5 additions & 0 deletions b/‎doc/api/next_api_changes/deprecations/26444-ES.rst
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diff --git a/‎lib/matplotlib/table.py
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+11-8Lines changed: 11 additions & 8 deletions b/‎lib/matplotlib/table.py
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+11-8Lines changed: 11 additions & 8 deletions
diff --git a/‎lib/matplotlib/tests/test_table.py
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+11-4Lines changed: 11 additions & 4 deletions b/‎lib/matplotlib/tests/test_table.py
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+11-4Lines changed: 11 additions & 4 deletions
@@ -0,0 +1,5 @@
+Passing non-int or sequence of non-int to ``Table.auto_set_column_width``
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Column numbers are ints, and formerly passing any other type was effectively
+ignored. This will become an error in the future.
@@ -24,6 +24,8 @@
 Thanks to John Gill for providing the class and table.
 """
 
+import numpy as np
+
 from . import _api, _docstring
 from .artist import Artist, allow_rasterization
 from .patches import Rectangle
@@ -494,14 +496,15 @@ def auto_set_column_width(self, col):
         col : int or sequence of ints
             The indices of the columns to auto-scale.
         """
-        # check for col possibility on iteration
-        try:
-            iter(col)
-        except (TypeError, AttributeError):
-            self._autoColumns.append(col)
-        else:
-            for cell in col:
-                self._autoColumns.append(cell)
+        col1d = np.atleast_1d(col)
+        if not np.issubdtype(col1d.dtype, np.integer):
+            _api.warn_deprecated("3.8", name="col",
+                                 message="%(name)r must be an int or sequence of ints. "
+                                 "Passing other types is deprecated since %(since)s "
+                                 "and will be removed %(removal)s.")
+            return
+        for cell in col1d:
+            self._autoColumns.append(cell)
 
         self.stale = True
 
 
@@ -1,9 +1,11 @@
-import matplotlib.pyplot as plt
 import numpy as np
-from matplotlib.testing.decorators import image_comparison, check_figures_equal
+import pytest
 
-from matplotlib.table import CustomCell, Table
+import matplotlib.pyplot as plt
+import matplotlib as mpl
 from matplotlib.path import Path
+from matplotlib.table import CustomCell, Table
+from matplotlib.testing.decorators import image_comparison, check_figures_equal
 from matplotlib.transforms import Bbox
 
 
@@ -176,7 +178,12 @@ def test_auto_column():
         loc="center")
     tb4.auto_set_font_size(False)
     tb4.set_fontsize(12)
-    tb4.auto_set_column_width("-101")
+    with pytest.warns(mpl.MatplotlibDeprecationWarning,
+                      match="'col' must be an int or sequence of ints"):
+        tb4.auto_set_column_width("-101")  # type: ignore [arg-type]
+    with pytest.warns(mpl.MatplotlibDeprecationWarning,
+                      match="'col' must be an int or sequence of ints"):
+        tb4.auto_set_column_width(["-101"])  # type: ignore [list-item]
 
 
 def test_table_cells():