Allowing hover_data and custom_data to pass string of column name instead of requiring a list.

packages/python/plotly/plotly/express/_core.py

@@ -1295,11 +1295,14 @@ def build_dataframe(args, constructor):
     # make copies of all the fields via dict() and list()
     for field in args:
         if field in array_attrables and args[field] is not None:
-            args[field] = (
-                dict(args[field])
-                if isinstance(args[field], dict)
-                else list(args[field])
-            )
+            if isinstance(args[field], dict):
+                args[field] = dict(args[field])
+            elif field in ["custom_data", "hover_data"] and isinstance(
+                args[field], str
+            ):
+                args[field] = [args[field]]
+            else:
+                args[field] = list(args[field])
 
     # Cast data_frame argument to DataFrame (it could be a numpy array, dict etc.)
     df_provided = args["data_frame"] is not None

packages/python/plotly/plotly/express/_doc.py

@@ -199,8 +199,8 @@
         "Values from this column or array_like appear in bold in the hover tooltip.",
     ],
     hover_data=[
-        "list of str or int, or Series or array-like, or dict",
-        "Either a list of names of columns in `data_frame`, or pandas Series,",
+        "str, or list of str or int, or Series or array-like, or dict",
+        "Either a name or list of names of columns in `data_frame`, or pandas Series,",
         "or array_like objects",
         "or a dict with column names as keys, with values True (for default formatting)",
         "False (in order to remove this column from hover information),",
@@ -211,8 +211,8 @@
         "Values from these columns appear as extra data in the hover tooltip.",
     ],
     custom_data=[
-        colref_list_type,
-        colref_list_desc,
+        "str, or list of str or int, or Series or array-like",
+        "Either name or list of names of columns in `data_frame`, or pandas Series, or array_like objects",
         "Values from these columns are extra data, to be used in widgets or Dash callbacks for example. This data is not user-visible but is included in events emitted by the figure (lasso selection etc.)",
     ],
     text=[

packages/python/plotly/plotly/tests/test_optional/test_px/test_px_hover.py

@@ -17,6 +17,17 @@ def test_skip_hover():
     assert fig.data[0].hovertemplate == "species_id=%{marker.size}<extra></extra>"
 
 
+def test_hover_data_string_column():
+    df = px.data.tips()
+    fig = px.scatter(
+        df,
+        x="tip",
+        y="total_bill",
+        hover_data="sex",
+    )
+    assert "sex" in fig.data[0].hovertemplate
+
+
 def test_composite_hover():
     df = px.data.tips()
     hover_dict = OrderedDict(
@@ -89,17 +100,20 @@ def test_formatted_hover_and_labels():
 
 
 def test_fail_wrong_column():
-    with pytest.raises(ValueError) as err_msg:
-        px.scatter(
-            {"a": [1, 2], "b": [3, 4], "c": [2, 1]},
-            x="a",
-            y="b",
-            hover_data={"d": True},
+    # Testing for each of bare string, list, and basic dictionary
+    for hover_data_value in ["d", ["d"], {"d": True}]:
+        with pytest.raises(ValueError) as err_msg:
+            px.scatter(
+                {"a": [1, 2], "b": [3, 4], "c": [2, 1]},
+                x="a",
+                y="b",
+                hover_data=hover_data_value,
+            )
+        assert (
+            "Value of 'hover_data_0' is not the name of a column in 'data_frame'."
+            in str(err_msg.value)
         )
-    assert (
-        "Value of 'hover_data_0' is not the name of a column in 'data_frame'."
-        in str(err_msg.value)
-    )
+    # Testing other dictionary possibilities below
     with pytest.raises(ValueError) as err_msg:
         px.scatter(
             {"a": [1, 2], "b": [3, 4], "c": [2, 1]},