Fix showing "None" as ylabel in :meth:Series.plot when not setting ylabel (#46445)

Author: iansheng

doc/source/whatsnew/v1.5.0.rst

@@ -110,6 +110,13 @@ did not have the same index as the input.
     df.groupby('a', dropna=True).transform(lambda x: x)
     df.groupby('a', dropna=True).transform('sum')
 
+.. _whatsnew_150.notable_bug_fixes.visualization:
+
+Styler
+^^^^^^
+
+- Fix showing "None" as ylabel in :meth:`Series.plot` when not setting ylabel (:issue:`46129`)
+
 .. _whatsnew_150.notable_bug_fixes.notable_bug_fix2:
 
 notable_bug_fix2

pandas/plotting/_matplotlib/core.py

@@ -458,7 +458,7 @@ def _compute_plot_data(self):
         if isinstance(data, ABCSeries):
             label = self.label
             if label is None and data.name is None:
-                label = "None"
+                label = ""
             if label is None:
                 # We'll end up with columns of [0] instead of [None]
                 data = data.to_frame()

pandas/tests/plotting/frame/test_frame.py

@@ -1188,7 +1188,7 @@ def test_line_label_none(self):
         assert ax.get_legend() is None
 
         ax = s.plot(legend=True)
-        assert ax.get_legend().get_texts()[0].get_text() == "None"
+        assert ax.get_legend().get_texts()[0].get_text() == ""
 
     @pytest.mark.parametrize(
         "props, expected",

pandas/tests/plotting/test_series.py

@@ -179,7 +179,7 @@ def test_label(self):
         self.plt.close()
         _, ax = self.plt.subplots()
         ax = s.plot(legend=True, ax=ax)
-        self._check_legend_labels(ax, labels=["None"])
+        self._check_legend_labels(ax, labels=[""])
         self.plt.close()
         # get name from index
         s.name = "NAME"