Add custom_data argument to px.histogram

CHANGELOG.md

@@ -4,6 +4,9 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Unreleased
 
+### Added
+- Add the `custom_data` argument to `px.histogram`, so extra columns can be attached to histogram traces for use in Dash callbacks and selection events, as in the other Plotly Express functions [[#3859](https://github.com/plotly/plotly.py/issues/3859)]
+
 ### Fixed
 - Fix `mpl_to_plotly` tick marker mirroring, axis positioning, and trace visibility for twinned and overlaid subplots (such as `twinx` and `twiny`) [[#5310](https://github.com/plotly/plotly.py/pull/5310)], with thanks to @robertoffmoura for the contribution!
 - Fix `mpl_to_plotly` losing matplotlib axis line colors by exporting the color of each axis's displayed spine to the plotly x and y axis `linecolor` [[#5311](https://github.com/plotly/plotly.py/pull/5311)], with thanks to @robertoffmoura for the contribution!

plotly/express/_chart_types.py

@@ -462,6 +462,7 @@ def histogram(
     facet_col_spacing=None,
     hover_name=None,
     hover_data=None,
+    custom_data=None,
     animation_frame=None,
     animation_group=None,
     category_orders=None,

tests/test_optional/test_px/test_px.py

@@ -68,6 +68,28 @@ def test_custom_data_scatter(backend):
     )
 
 
+def test_custom_data_histogram(backend):
+    tips = nw.from_native(px.data.tips(return_type=backend))
+    # No custom data
+    fig = px.histogram(tips.to_native(), x="total_bill")
+    assert fig.data[0].customdata is None
+    # Custom data is carried per row of the input, not per bin
+    fig = px.histogram(tips.to_native(), x="total_bill", custom_data=["tip", "day"])
+    assert fig.data[0].customdata.shape == (len(tips), 2)
+    assert np.all(fig.data[0].customdata[:, 0] == tips.get_column("tip").to_numpy())
+    assert np.all(fig.data[0].customdata[:, 1] == tips.get_column("day").to_numpy())
+    # Bins are aggregates, so custom data does not show up in the hover label
+    assert fig.data[0].hovertemplate == "total_bill=%{x}<br>count=%{y}<extra></extra>"
+    # Each colored trace carries the custom data of its own rows
+    fig = px.histogram(
+        tips.to_native(), x="total_bill", color="sex", custom_data=["tip"]
+    )
+    for trace in fig.data:
+        group = tips.filter(nw.col("sex") == trace.name)
+        assert trace.customdata.shape == (len(group), 1)
+        assert np.all(trace.customdata[:, 0] == group.get_column("tip").to_numpy())
+
+
 def test_labels(backend):
     tips = nw.from_native(px.data.tips(return_type=backend))
     fig = px.scatter(