Add formatting string argument to Text mark

doc/_docstrings/objects.Text.ipynb

@@ -155,12 +155,34 @@
     ")"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "ee2597dc",
+   "metadata": {},
+   "source": [
+    "Use `fmt` to format the text before display:"
+   ]
+  },
   {
    "cell_type": "code",
    "execution_count": null,
    "id": "95fb7aee-090a-4415-917c-b5258d2b298b",
    "metadata": {},
    "outputs": [],
+   "source": [
+    "(\n",
+    "    so.Plot(glue, x=\"Average\", y=\"Model\", text=\"Average\")\n",
+    "    .add(so.Bar())\n",
+    "    .add(so.Text(color=\"w\", halign=\"right\", fmt=\"{:.0f}\"))\n",
+    ")\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "87db5959",
+   "metadata": {},
+   "outputs": [],
    "source": []
   }
  ],

seaborn/_marks/text.py

@@ -36,6 +36,7 @@ class Text(Mark):
     halign: MappableString = Mappable("center")
     valign: MappableString = Mappable("center_baseline")
     offset: MappableFloat = Mappable(4)
+    fmt: str = "{}"
 
     def _plot(self, split_gen, scales, orient):
 
@@ -61,7 +62,7 @@ def _plot(self, split_gen, scales, orient):
                 artist = mpl.text.Text(
                     x=row["x"],
                     y=row["y"],
-                    text=str(row.get("text", vals["text"])),
+                    text=self.fmt.format(row.get("text", vals["text"])),
                     color=color,
                     fontsize=fontsize,
                     horizontalalignment=halign,

tests/_marks/test_text.py

@@ -127,3 +127,9 @@ def test_offset_halign(self):
         for text in self.get_texts(ax):
             shift_matrix = text.get_transform().get_matrix() - ax_trans
             assert_array_almost_equal(shift_matrix, expected_shift_matrix)
+
+    def test_fmt(self):
+        m = Text(fmt="{:.2f}")
+        p = Plot(x=[0], y=[0], text=[1.234]).add(m).plot()
+        ax = p._figure.axes[0]
+        assert self.get_texts(ax)[0].get_text() == "1.23"