factor out mark_right

Author: MarcoGorelli

pandas/plotting/_matplotlib/core.py

@@ -579,11 +579,17 @@ def legend_title(self) -> Optional[str]:
             stringified = map(pprint_thing, self.data.columns.names)
             return ",".join(stringified)
 
-    def _add_legend_handle(self, handle, label, index=None):
+    def _mark_right_label(
+        self, label: Optional[str], index: Optional[int]
+    ) -> Optional[str]:
         if label is not None:
             if self.mark_right and index is not None:
                 if self.on_right(index):
                     label = label + " (right)"
+        return label
+
+    def _add_legend_handle(self, handle: Artist, label: str) -> None:
+        if label is not None:
             self.legend_handles.append(handle)
             self.legend_labels.append(label)
 
@@ -1065,7 +1071,6 @@ def _make_plot(self):
             label = self.label
         else:
             label = None
-
         scatter = ax.scatter(
             data[x].values,
             data[y].values,
@@ -1175,6 +1180,7 @@ def _make_plot(self):
             kwds = dict(kwds, **errors)
 
             label = pprint_thing(label)  # .encode('utf-8')
+            label = self._mark_right_label(label, i)
             kwds["label"] = label
 
             newlines = plotf(
@@ -1187,8 +1193,7 @@ def _make_plot(self):
                 is_errorbar=is_errorbar,
                 **kwds,
             )
-            if label is not None:
-                self._add_legend_handle(newlines[0], label, index=i)
+            self._add_legend_handle(newlines[0], label)
 
             if self._is_ts_plot():
 
@@ -1464,11 +1469,7 @@ def _make_plot(self):
             kwds = dict(kwds, **errors)
 
             label = pprint_thing(label)
-
-            if label is not None:
-                if self.mark_right and i is not None:
-                    if self.on_right(i):
-                        label = label + " (right)"
+            label = self._mark_right_label(label, i)
 
             if (("yerr" in kwds) or ("xerr" in kwds)) and (kwds.get("ecolor") is None):
                 kwds["ecolor"] = mpl.rcParams["xtick.color"]
@@ -1519,8 +1520,7 @@ def _make_plot(self):
                     log=self.log,
                     **kwds,
                 )
-            if label is not None:
-                self._add_legend_handle(rect, label, index=i)
+            self._add_legend_handle(rect, label)
 
     def _post_plot_logic(self, ax: Axes, data):
         if self.use_index:

pandas/plotting/_matplotlib/hist.py

@@ -89,6 +89,7 @@ def _make_plot(self):
             kwds = self.kwds.copy()
 
             label = pprint_thing(label)
+            label = self._mark_right_label(label, i)
             kwds["label"] = label
 
             style, kwds = self._apply_style_colors(colors, kwds, i, label)
@@ -105,7 +106,7 @@ def _make_plot(self):
                 kwds["weights"] = weights[:, i]
 
             artists = self._plot(ax, y, column_num=i, stacking_id=stacking_id, **kwds)
-            self._add_legend_handle(artists[0], label, index=i)
+            self._add_legend_handle(artists[0], label)
 
     def _make_plot_keywords(self, kwds, y):
         """merge BoxPlot/KdePlot properties to passed kwds"""