Automatically use y as default 'text' kwarg if only two cols (#1681)

Author: ahuang11

hvplot/converter.py

@@ -3038,7 +3038,7 @@ def labels(self, x=None, y=None, data=None):
 
         text = self.kwds.get('text')
         if not text:
-            text = [c for c in data.columns if c not in (x, y)][0]
+            text = next((c for c in data.columns if c not in (x, y)), y)
         elif text not in data.columns:
             data = data.copy()
             template_str = text  # needed for dask lazy compute

hvplot/tests/testcharts.py

@@ -535,6 +535,17 @@ def test_labels_format_float(self):
         ]
         assert list(plot.data['label']) == ['-58.7E -34.58N', '-47.9E -15.78N', '-70.7E -33.45N']
 
+    def test_labels_default_y(self):
+        edge_df = self.edge_df.copy().drop(columns=['Volume {m3}'])
+        plot = edge_df.hvplot.labels('Longitude', 'Latitude')
+        assert list(plot.dimensions()) == [
+            Dimension('Longitude'),
+            Dimension('Latitude'),
+            Dimension('Latitude'),
+        ]
+        assert plot.kdims == ['Longitude', 'Latitude']
+        assert plot.vdims == ['Latitude']
+
     def test_labels_by(self):
         plot = self.edge_df.hvplot.labels(
             'Longitude', 'Latitude', text='{Longitude:.1f}E {Latitude:.2f}N', by='Volume {m3}'