hover can be a dict for skipping or formatting hover

Author: emmanuelle

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

@@ -290,7 +290,10 @@ def make_trace_kwargs(args, trace_spec, trace_data, mapping_labels, sizeref):
                     go.Histogram2d,
                     go.Histogram2dContour,
                 ]:
+                    hover_is_dict = isinstance(attr_value, dict)
                     for col in attr_value:
+                        if hover_is_dict and not attr_value[col]:
+                            continue
                         try:
                             position = args["custom_data"].index(col)
                         except (ValueError, AttributeError, KeyError):
@@ -387,7 +390,20 @@ def make_trace_kwargs(args, trace_spec, trace_data, mapping_labels, sizeref):
         go.Parcoords,
         go.Parcats,
     ]:
-        hover_lines = [k + "=" + v for k, v in mapping_labels.items()]
+        # Modify mapping_labels according to hover_data keys
+        # if hover_data is a dict
+        mapping_labels_copy = OrderedDict(mapping_labels)
+        if args["hover_data"] and isinstance(args["hover_data"], dict):
+            for k, v in mapping_labels.items():
+                if k in args["hover_data"]:
+                    if args["hover_data"][k]:
+                        if isinstance(args["hover_data"][k], str):
+                            mapping_labels_copy[k] = v.replace(
+                                "}", ":%s}" % args["hover_data"][k]
+                            )
+                    else:
+                        _ = mapping_labels_copy.pop(k)
+        hover_lines = [k + "=" + v for k, v in mapping_labels_copy.items()]
         trace_patch["hovertemplate"] = hover_header + "<br>".join(hover_lines)
         trace_patch["hovertemplate"] += "<extra></extra>"
     return trace_patch, fit_results
@@ -1029,6 +1045,8 @@ def build_dataframe(args, attrables, array_attrables):
             # Finally, update argument with column name now that column exists
             if field_name not in array_attrables:
                 args[field_name] = str(col_name)
+            elif isinstance(args[field_name], dict):
+                pass
             else:
                 args[field_name][i] = str(col_name)
 

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

@@ -180,8 +180,12 @@
         "Values from this column or array_like appear in bold in the hover tooltip.",
     ],
     hover_data=[
-        colref_list_type,
-        colref_list_desc,
+        "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,",
+        "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),",
+        "or a formatting string, for example '.3f'."
         "Values from these columns appear as extra data in the hover tooltip.",
     ],
     custom_data=[

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

@@ -0,0 +1,33 @@
+import plotly.express as px
+import numpy as np
+import pandas as pd
+import pytest
+import plotly.graph_objects as go
+
+
+def test_skip_hover():
+    df = px.data.iris()
+    fig = px.scatter(
+        df,
+        x="petal_length",
+        y="petal_width",
+        size="species_id",
+        hover_data={"petal_length": None, "petal_width": None},
+    )
+    assert fig.data[0].hovertemplate == "species_id=%{marker.size}<extra></extra>"
+
+
+def test_composite_hover():
+    df = px.data.tips()
+    fig = px.scatter(
+        df,
+        x="tip",
+        y="total_bill",
+        color="day",
+        facet_row="time",
+        hover_data={"day": False, "sex": True, "time": False, "total_bill": ".1f"},
+    )
+    assert (
+        fig.data[0].hovertemplate
+        == "tip=%{x}<br>total_bill=%{customdata[1]:.1f}<br>sex=%{customdata[0]}<extra></extra>"
+    )