Title check checks for subplot length if specified

Author: eicchen

pandas/plotting/_matplotlib/core.py

@@ -802,7 +802,16 @@ def _adorn_subplots(self, fig: Figure) -> None:
         if self.title:
             if self.subplots:
                 if is_list_like(self.title):
-                    if len(self.title) != self.nseries:
+                    if type(self.subplots) != bool:
+                        if len(self.subplots) != len(self.title):
+                            raise ValueError(
+                                "The length of `title` must equal the number "
+                                "of subplots if `title` of type `list` "
+                                "and subplots is iterable.\n"
+                                f"length of title = {len(self.title)}\n"
+                                f"number of subplots = {len(self.subplots)}"
+                            )
+                    elif len(self.title) != self.nseries:
                         raise ValueError(
                             "The length of `title` must equal the number "
                             "of columns if using `title` of type `list` "

pandas/tests/plotting/test_misc.py

@@ -829,8 +829,9 @@ def test_plot_bar_label_count_expected_fail():
     )
     with pytest.raises(
         ValueError,
-        match="The length of `title` must equal the number of columns "
-        "if using `title` of type `list` and `subplots=True`.",
+        match="The length of `title` must equal the number "
+        "of subplots if `title` of type `list` "
+        "and subplots is iterable.\n",
     ):
         df.plot(
             subplots=[("A", "B")],