Default cell formatter fixes

docs/examples/widgets/data_table.py

@@ -1,18 +1,18 @@
-import csv
-import io
-
 from textual.app import App, ComposeResult
 from textual.widgets import DataTable
 
-CSV = """lane,swimmer,country,time
-4,Joseph Schooling,Singapore,50.39
-2,Michael Phelps,United States,51.14
-5,Chad le Clos,South Africa,51.14
-6,László Cseh,Hungary,51.14
-3,Li Zhuhao,China,51.26
-8,Mehdy Metella,France,51.58
-7,Tom Shields,United States,51.73
-1,Aleksandr Sadovnikov,Russia,51.84"""
+ROWS = [
+    ("lane", "swimmer", "country", "time"),
+    (4, "Joseph Schooling", "Singapore", 50.39),
+    (2, "Michael Phelps", "United States", 51.14),
+    (5, "Chad le Clos", "South Africa", 51.14),
+    (6, "László Cseh", "Hungary", 51.14),
+    (3, "Li Zhuhao", "China", 51.26),
+    (8, "Mehdy Metella", "France", 51.58),
+    (7, "Tom Shields", "United States", 51.73),
+    (1, "Aleksandr Sadovnikov", "Russia", 51.84),
+    (10, "Darren Burns", "Scotland", 51.84),
+]
 
 
 class TableApp(App):
@@ -21,7 +21,7 @@ class TableApp(App):
 
     def on_mount(self) -> None:
         table = self.query_one(DataTable)
-        rows = csv.reader(io.StringIO(CSV))
+        rows = iter(ROWS)
         table.add_columns(*next(rows))
         table.add_rows(rows)
 

src/textual/widgets/_data_table.py

@@ -88,19 +88,21 @@ class CellKey(NamedTuple):
     column_key: ColumnKey | str
 
 
-def default_cell_formatter(obj: object) -> RenderableType | None:
+def default_cell_formatter(obj: object) -> RenderableType:
     """Format a cell in to a renderable.
 
     Args:
         obj: Data for a cell.
 
     Returns:
-        A renderable or None if the object could not be rendered.
+        A renderable to be displayed which represents the data.
     """
     if isinstance(obj, str):
         return Text.from_markup(obj)
+    if isinstance(obj, float):
+        return f"{obj:.2f}"
     if not is_renderable(obj):
-        return None
+        return str(obj)
     return cast(RenderableType, obj)