Use sensible defaults for BarRenderer.bar_value

Signed-off-by: Ian Thomas <[email protected]>

Author: ianthomas23

examples/ConditionalFormatting.ipynb

@@ -340,7 +340,7 @@
     "renderers = {\n",
     "    \"Value 1\": text_renderer,\n",
     "    \"Dates\": BarRenderer(\n",
-    "        bar_value=DateScale(min=df[\"Dates\"][0], max=df[\"Dates\"][n - 1]),\n",
+    "        bar_value=DateScale(),\n",
     "        bar_color=Expr(bar_color),\n",
     "        format=\"%Y/%m/%d\",\n",
     "        format_type=\"time\",\n",

examples/Pandas.ipynb

@@ -47,7 +47,7 @@
     "    \"Value 1\": text_renderer,\n",
     "    \"Value 2\": text_renderer,\n",
     "    \"Dates\": BarRenderer(\n",
-    "        bar_value=DateScale(min=df[\"Dates\"][0], max=df[\"Dates\"][n - 1]),\n",
+    "        bar_value=DateScale(),\n",
     "        bar_color=Expr(bar_color),\n",
     "        format=\"%Y/%m/%d\",\n",
     "        format_type=\"time\",\n",

ipydatagrid/cellrenderer.py

@@ -120,7 +120,8 @@ class BarRenderer(TextRenderer):
     _view_name = Unicode("BarRendererView").tag(sync=True)
 
     bar_value = Union(
-        (Float(), Instance(VegaExpr), Instance(Scale)), default_value=0.0
+        (Float(allow_none=True), Instance(VegaExpr), Instance(Scale)),
+        default_value=0.0,
     ).tag(sync=True, **widget_serialization)
     bar_color = Union(
         (Color(), Instance(VegaExpr), Instance(ColorScale)),

ipydatagrid/datagrid.py

@@ -23,7 +23,7 @@
 )
 
 from ._frontend import module_name, module_version
-from .cellrenderer import CellRenderer, TextRenderer
+from .cellrenderer import BarRenderer, CellRenderer, TextRenderer
 
 
 class SelectionIterator(Iterator):
@@ -378,6 +378,7 @@ def __init__(self, dataframe, index_name=None, **kwargs):
         self._cell_click_handlers = CallbackDispatcher()
         self._cell_change_handlers = CallbackDispatcher()
         self.on_msg(self.__handle_custom_msg)
+        self._set_renderer_defaults()
 
     def __handle_custom_msg(self, _, content, buffers):  # noqa: U101,U100
         if content["event_type"] == "cell-changed":
@@ -865,3 +866,47 @@ def _get_cell_value_by_numerical_index(data, column_index, row_index):
         if column is None:
             return None
         return data["data"][row_index][column]
+
+    def _set_renderer_defaults(self):
+        # Set sensible default values for renderers that are not completely
+        # specified, such as missing a min or max value.
+
+        data = None  # Only read data once, and only if necessary.
+
+        for name, renderer in self.renderers.items():
+            if isinstance(renderer, BarRenderer):
+                from bqplot import DateScale, LinearScale, Scale
+
+                if renderer.bar_value is None:
+                    # If BarRenderer.bar_value is not specified, create an
+                    # appropriate Scale based on the column data type.
+                    col_schema = next(
+                        filter(
+                            lambda x: x["name"] == name,
+                            self._data["schema"]["fields"],
+                        )
+                    )
+                    is_date = col_schema["type"] in ("date", "time", "datetime")
+                    if is_date:
+                        renderer.bar_value = DateScale()
+                    else:
+                        renderer.bar_value = LinearScale()
+
+                scale = renderer.bar_value
+                if (
+                    isinstance(scale, Scale)
+                    and scale.has_trait("min")
+                    and scale.has_trait("max")
+                    and (scale.min is None or scale.max is None)
+                ):
+                    # Set min and/or max from column data.
+                    if data is None:
+                        data = self.data  # Only want to get the data once
+                    column_data = data[name]
+                    is_date = isinstance(scale, DateScale)
+                    if scale.min is None:
+                        min = column_data.min()
+                        scale.min = min if is_date else float(min)
+                    if scale.max is None:
+                        max = column_data.max()
+                        scale.max = max if is_date else float(max)

tests/test_datagrid.py

@@ -3,8 +3,9 @@
 import numpy as np
 import pandas as pd
 import pytest
+from bqplot import DateScale, LinearScale, LogScale
 
-from ipydatagrid import DataGrid, TextRenderer
+from ipydatagrid import BarRenderer, DataGrid, TextRenderer
 from ipydatagrid.datagrid import _widgets_dict_serialization
 
 
@@ -15,6 +16,13 @@ def dataframe() -> pd.DataFrame:
     )
 
 
+@pytest.fixture()
+def dataframe_with_datetime(dataframe) -> pd.DataFrame:
+    return dataframe.assign(
+        dates=pd.to_datetime(["2024-03-05", "2024-03-06", "2024-03-07"])
+    )
+
+
 @pytest.fixture()
 def datagrid(dataframe) -> DataGrid:
     return DataGrid(dataframe)
@@ -307,3 +315,39 @@ def test_serialization():
     dg = DataGrid(df)
 
     assert dg.data.to_json() == df.to_json()
+
+
+@pytest.mark.parametrize(
+    ("column", "bar_value", "expected_min", "expected_max"),
+    [
+        ("B", None, 4.0, 6.0),
+        ("B", LinearScale(), 4.0, 6.0),
+        ("B", LinearScale(min=2.2), 2.2, 6.0),
+        ("B", LinearScale(max=4.4), 4.0, 4.4),
+        ("B", LogScale(), 4.0, 6.0),
+        (
+            "dates",
+            DateScale(),
+            pd.Timestamp("2024-03-05"),
+            pd.Timestamp("2024-03-07"),
+        ),
+    ],
+)
+def test_bar_renderer_defaults(
+    dataframe_with_datetime,
+    column,
+    bar_value,
+    expected_min,
+    expected_max,
+):
+    expected_type = type(bar_value) if bar_value else LinearScale
+
+    grid = DataGrid(
+        dataframe_with_datetime,
+        renderers={column: BarRenderer(bar_value=bar_value)},
+    )
+
+    actual_bar_value = grid.renderers[column].bar_value
+    assert isinstance(actual_bar_value, expected_type)
+    assert actual_bar_value.min == expected_min
+    assert actual_bar_value.max == expected_max

ui-tests-ipw7/tests/notebooks/conditional_formatting.ipynb

@@ -291,7 +291,7 @@
     "renderers = {\n",
     "    \"Value 1\": text_renderer,\n",
     "    \"Dates\": BarRenderer(\n",
-    "        bar_value=DateScale(min=df[\"Dates\"][0], max=df[\"Dates\"][n - 1]),\n",
+    "        bar_value=DateScale(),\n",
     "        bar_color=Expr(bar_color),\n",
     "        format=\"%Y/%m/%d\",\n",
     "        format_type=\"time\",\n",

ui-tests-ipw7/tests/notebooks/datagrid.ipynb

@@ -42,7 +42,7 @@
     "    \"Value 1\": text_renderer,\n",
     "    \"Value 2\": text_renderer,\n",
     "    \"Dates\": BarRenderer(\n",
-    "        bar_value=DateScale(min=df[\"Dates\"][0], max=df[\"Dates\"][n - 1]),\n",
+    "        bar_value=DateScale(),\n",
     "        bar_color=Expr(bar_color),\n",
     "        format=\"%Y/%m/%d\",\n",
     "        format_type=\"time\",\n",

ui-tests-ipw8/tests/notebooks/conditional_formatting.ipynb

@@ -291,7 +291,7 @@
     "renderers = {\n",
     "    \"Value 1\": text_renderer,\n",
     "    \"Dates\": BarRenderer(\n",
-    "        bar_value=DateScale(min=df[\"Dates\"][0], max=df[\"Dates\"][n - 1]),\n",
+    "        bar_value=DateScale(),\n",
     "        bar_color=Expr(bar_color),\n",
     "        format=\"%Y/%m/%d\",\n",
     "        format_type=\"time\",\n",

ui-tests-ipw8/tests/notebooks/datagrid.ipynb

@@ -42,7 +42,7 @@
     "    \"Value 1\": text_renderer,\n",
     "    \"Value 2\": text_renderer,\n",
     "    \"Dates\": BarRenderer(\n",
-    "        bar_value=DateScale(min=df[\"Dates\"][0], max=df[\"Dates\"][n - 1]),\n",
+    "        bar_value=DateScale(),\n",
     "        bar_color=Expr(bar_color),\n",
     "        format=\"%Y/%m/%d\",\n",
     "        format_type=\"time\",\n",