time format

Author: willmcgugan

CHANGELOG.md

@@ -15,11 +15,12 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - Buttons may not be pressed within their "active_effect_duration" to prevent inadvertent activations https://github.com/Textualize/textual/pull/4621
 - `Screen.dismiss` is now a noop if the screen isn't active. Previously it would raise a `ScreenStackError`, now it returns `False`. https://github.com/Textualize/textual/pull/4621
 - Increased window for escape processing to 100ms
-- Added `icon` reactive to Header widget
 
 ### Added
 
 - Added `Screen.is_active` 
+- Added `icon` reactive to Header widget https://github.com/Textualize/textual/pull/4627
+- Added `time_format` reactive to Header widget https://github.com/Textualize/textual/pull/4627
 
 ## [0.65.2] - 2023-06-06
 

src/textual/widgets/_header.py

@@ -77,6 +77,8 @@ class HeaderClock(HeaderClockSpace):
     }
     """
 
+    time_format: Reactive[str] = Reactive("%X")
+
     def _on_mount(self, _: Mount) -> None:
         self.set_interval(1, callback=self.refresh, name=f"update header clock")
 
@@ -86,7 +88,7 @@ def render(self) -> RenderResult:
         Returns:
             The rendered clock.
         """
-        return Text(datetime.now().time().strftime("%X"))
+        return Text(datetime.now().time().strftime(self.time_format))
 
 
 class HeaderTitle(Widget):
@@ -142,6 +144,9 @@ class Header(Widget):
     icon: Reactive[str] = Reactive("⭘")
     """A character for the icon at the top left."""
 
+    time_format: Reactive[str] = Reactive("%X")
+    """Time format of the clock."""
+
     def __init__(
         self,
         show_clock: bool = False,
@@ -150,6 +155,7 @@ def __init__(
         id: str | None = None,
         classes: str | None = None,
         icon: str | None = None,
+        time_format: str | None = None,
     ):
         """Initialise the header widget.
 
@@ -158,16 +164,24 @@ def __init__(
             name: The name of the header widget.
             id: The ID of the header widget in the DOM.
             classes: The CSS classes of the header widget.
+            icon: Single character to use as an icon, or `None` for default.
+            time_format: Time format (used by strftime) for clock, or `None` for default.
         """
         super().__init__(name=name, id=id, classes=classes)
         self._show_clock = show_clock
         if icon is not None:
             self.icon = icon
+        if time_format is not None:
+            self.time_format = time_format
 
     def compose(self):
         yield HeaderIcon().data_bind(Header.icon)
         yield HeaderTitle()
-        yield HeaderClock() if self._show_clock else HeaderClockSpace()
+        yield (
+            HeaderClock().data_bind(Header.time_format)
+            if self._show_clock
+            else HeaderClockSpace()
+        )
 
     def watch_tall(self, tall: bool) -> None:
         self.set_class(tall, "-tall")