Start fleshing out a RadioSet widget

Much more to do with this, but I just wanted to get a feel for the core
working.

src/textual/widgets/__init__.py

@@ -24,6 +24,7 @@ if typing.TYPE_CHECKING:
     from ._placeholder import Placeholder
     from ._pretty import Pretty
     from ._radio_button import RadioButton
+    from ._radio_set import RadioSet
     from ._static import Static
     from ._switch import Switch
     from ._text_log import TextLog
@@ -47,6 +48,7 @@ __all__ = [
     "Placeholder",
     "Pretty",
     "RadioButton",
+    "RadioSet",
     "Static",
     "Switch",
     "TextLog",

src/textual/widgets/__init__.pyi

@@ -14,6 +14,7 @@ from ._markdown import MarkdownViewer as MarkdownViewer
 from ._placeholder import Placeholder as Placeholder
 from ._pretty import Pretty as Pretty
 from ._radio_button import RadioButton as RadioButton
+from ._radio_set import RadioSet as RadioSet
 from ._static import Static as Static
 from ._switch import Switch as Switch
 from ._text_log import TextLog as TextLog

src/textual/widgets/_radio_set.py

@@ -0,0 +1,39 @@
+"""Provides a RadioSet widget, which groups radio buttons."""
+
+from __future__ import annotations
+
+from ..containers import Container
+from ._radio_button import RadioButton
+
+
+class RadioSet(Container):
+    """Widget for grouping a collection of radio buttons into a set."""
+
+    def __init__(self, *buttons: str | RadioButton) -> None:
+        """Initialise the radio set.
+
+        Args:
+            buttons: A collection of labels or `RadioButton`s to group together.
+
+        Note:
+            When a `str` label is provided, a `RadioButton` will be created from it.
+        """
+        self._buttons = [
+            (button if isinstance(button, RadioButton) else RadioButton(button))
+            for button in buttons
+        ]
+        super().__init__(*self._buttons)
+
+    def on_radio_button_selected(self, event: RadioButton.Selected) -> None:
+        """Respond to a radio button in the set being selected be the user.
+
+        Args:
+            event: The event being raised.
+        """
+        # For each of the buttons we're responsible for...
+        for button in self._buttons:
+            # ...if it's on and it's not the selected button...
+            if button.value and button != event.input:
+                # ...turn it off.
+                button.value = False
+                break