fix facet labels

Author: nicolaskruchten

Diff for: packages/python/plotly/plotly/express/_core.py

@@ -1267,7 +1267,9 @@ def make_figure(args, constructor, trace_patch={}, layout_patch={}):
                 if m.facet == "row":
                     row = m.val_map[val]
                     if args["facet_row"] and len(row_labels) < row:
-                        row_labels.append(args["facet_row"] + "=" + str(val))
+                        row_labels.append(
+                            get_label(args, args["facet_row"]) + "=" + str(val)
+                        )
                 else:
                     if (
                         bool(args.get("marginal_x", False))
@@ -1282,7 +1284,9 @@ def make_figure(args, constructor, trace_patch={}, layout_patch={}):
                 if m.facet == "col":
                     col = m.val_map[val]
                     if args["facet_col"] and len(col_labels) < col:
-                        col_labels.append(args["facet_col"] + "=" + str(val))
+                        col_labels.append(
+                            get_label(args, args["facet_col"]) + "=" + str(val)
+                        )
                     if facet_col_wrap:  # assumes no facet_row, no marginals
                         row = 1 + ((col - 1) // facet_col_wrap)
                         col = 1 + ((col - 1) % facet_col_wrap)

Diff for: packages/python/plotly/plotly/tests/test_core/test_px/test_px.py

@@ -53,6 +53,30 @@ def test_custom_data_scatter():
     )
 
 
+def test_labels():
+    tips = px.data.tips()
+    fig = px.scatter(
+        tips,
+        x="total_bill",
+        y="tip",
+        facet_row="time",
+        facet_col="day",
+        color="size",
+        symbol="sex",
+        labels={c: c[::-1] for c in tips.columns},
+    )
+    assert "xes" in fig.data[0].hovertemplate
+    assert "llib_latot" in fig.data[0].hovertemplate
+    assert "ezis" in fig.data[0].hovertemplate
+    assert "yad" in fig.data[0].hovertemplate
+    assert "emit" in fig.data[0].hovertemplate
+    assert fig.data[0].name.startswith("xes")
+    assert fig.layout.xaxis.title.text == "llib_latot"
+    assert fig.layout.coloraxis.colorbar.title.text == "ezis"
+    assert fig.layout.annotations[0].text.startswith("yad")
+    assert fig.layout.annotations[4].text.startswith("emit")
+
+
 def test_px_templates():
     import plotly.io as pio
     import plotly.graph_objects as go