textual.app

Here you will find the App class, which is the base class for Textual apps.

See app basics for how to build Textual apps.

AutopilotCallbackType module-attribute

AutopilotCallbackType = (
    "Callable[[Pilot[object]], Coroutine[Any, Any, None]]"
)

Signature for valid callbacks that can be used to control apps.

ActionError

Bases: Exception

Base class for exceptions relating to actions.

ActiveModeError

Bases: ModeError

Raised when attempting to remove the currently active mode.

App

App(driver_class=None, css_path=None, watch_css=False)

Bases: Generic[ReturnType], DOMNode

The base class for Textual Applications.

Parameters:

Name	Type	Description	Default
driver_class	Type[Driver] | None	Driver class or None to auto-detect. This will be used by some Textual tools.	None
css_path	CSSPathType | None	Path to CSS or None to use the CSS_PATH class variable. To load multiple CSS files, pass a list of strings or paths which will be loaded in order.	None
watch_css	bool	Reload CSS if the files changed. This is set automatically if you are using textual run with the dev switch.	False

Raises:

Type	Description
CssPathError	When the supplied CSS path(s) are an unexpected type.

AUTO_FOCUS class-attribute

AUTO_FOCUS = '*'

A selector to determine what to focus automatically when a screen is activated.

The widget focused is the first that matches the given CSS selector. Setting to None or "" disables auto focus.

CLOSE_TIMEOUT class-attribute instance-attribute

CLOSE_TIMEOUT = 5.0

Timeout waiting for widget's to close, or None for no timeout.

COMMANDS class-attribute

COMMANDS = {get_system_commands}

Command providers used by the command palette.

Should be a set of command.Provider classes.

CSS class-attribute

CSS = ''

Inline CSS, useful for quick scripts. This is loaded after CSS_PATH, and therefore takes priority in the event of a specificity clash.

CSS_PATH class-attribute

CSS_PATH = None

File paths to load CSS from.

ENABLE_COMMAND_PALETTE class-attribute

ENABLE_COMMAND_PALETTE = True

Should the command palette be enabled for the application?

MODES class-attribute

MODES = {}

Modes associated with the app and their base screens.

The base screen is the screen at the bottom of the mode stack. You can think of it as the default screen for that stack. The base screens can be names of screens listed in SCREENS, Screen instances, or callables that return screens.

Example

class HelpScreen(Screen[None]):
    ...

class MainAppScreen(Screen[None]):
    ...

class MyApp(App[None]):
    MODES = {
        "default": "main",
        "help": HelpScreen,
    }

    SCREENS = {
        "main": MainAppScreen,
    }

    ...

NOTIFICATION_TIMEOUT class-attribute

NOTIFICATION_TIMEOUT = 5

Default number of seconds to show notifications before removing them.

SCREENS class-attribute

SCREENS = {}

Screens associated with the app for the lifetime of the app.

SUB_TITLE class-attribute instance-attribute

SUB_TITLE = None

A class variable to set the default sub-title for the application.

To update the sub-title while the app is running, you can set the sub_title attribute. See also the Screen.SUB_TITLE attribute.

TITLE class-attribute instance-attribute

TITLE = None

A class variable to set the default title for the application.

To update the title while the app is running, you can set the title attribute. See also the Screen.TITLE attribute.

active_bindings property

active_bindings

Get currently active bindings.

If no widget is focused, then app-level bindings are returned. If a widget is focused, then any bindings present in the active screen and app are merged and returned.

This property may be used to inspect current bindings.

Returns:

Type	Description
dict[str, ActiveBinding]	Active binding information

animation_level instance-attribute

animation_level = TEXTUAL_ANIMATIONS

Determines what type of animations the app will display.

See textual.constants.TEXTUAL_ANIMATIONS.

animator property

animator

The animator object.

ansi_theme property

ansi_theme

The ANSI TerminalTheme currently being used.

Defines how colors defined as ANSI (e.g. magenta) inside Rich renderables are mapped to hex codes.

ansi_theme_dark class-attribute instance-attribute

ansi_theme_dark = Reactive(MONOKAI, init=False)

Maps ANSI colors to hex colors using a Rich TerminalTheme object while in dark mode.

ansi_theme_light class-attribute instance-attribute

ansi_theme_light = Reactive(ALABASTER, init=False)

Maps ANSI colors to hex colors using a Rich TerminalTheme object while in light mode.

app_focus class-attribute instance-attribute

app_focus = Reactive(True, compute=False)

Indicates if the app has focus.

When run in the terminal, the app always has focus. When run in the web, the app will get focus when the terminal widget has focus.

app_resume_signal instance-attribute

app_resume_signal = Signal(self, 'app-resume')

The signal that is published when the app is resumed after a suspend.

When the app is resumed after a App.suspend call this signal will be published; subscribe to this signal to perform work after the app has resumed.

app_suspend_signal instance-attribute

app_suspend_signal = Signal(self, 'app-suspend')

The signal that is published when the app is suspended.

When App.suspend is called this signal will be published; subscribe to this signal to perform work before the suspension takes place.

children property

children

A view onto the app's immediate children.

This attribute exists on all widgets. In the case of the App, it will only ever contain a single child, which will be the currently active screen.

Returns:

Type	Description
Sequence['Widget']	A sequence of widgets.

current_mode property

current_mode

The name of the currently active mode.

cursor_position instance-attribute

cursor_position = Offset(0, 0)

The position of the terminal cursor in screen-space.

This can be set by widgets and is useful for controlling the positioning of OS IME and emoji popup menus.

dark class-attribute instance-attribute

dark = Reactive(True, compute=False)

Use a dark theme if True, otherwise use a light theme.

Modify this attribute to switch between light and dark themes.

Example

self.app.dark = not self.app.dark  # Toggle dark mode

debug property

debug

Is debug mode enabled?

focused property

focused

The widget that is focused on the currently active screen, or None.

Focused widgets receive keyboard input.

Returns:

Type	Description
Widget | None	The currently focused widget, or None if nothing is focused.

is_attached property

is_attached

Is this node linked to the app through the DOM?

is_dom_root property

is_dom_root

Is this a root node (i.e. the App)?

is_headless property

is_headless

Is the app running in 'headless' mode?

Headless mode is used when running tests with run_test.

is_inline property

is_inline

Is the app running in 'inline' mode?

log property

log

The textual logger.

Example

self.log("Hello, World!")
self.log(self.tree)

Returns:

Type	Description
Logger	A Textual logger.

return_code property

return_code

The return code with which the app exited.

Non-zero codes indicate errors. A value of 1 means the app exited with a fatal error. If the app hasn't exited yet, this will be None.

Example

The return code can be used to exit the process via sys.exit.

my_app.run()
sys.exit(my_app.return_code)

return_value property

return_value

The return value of the app, or None if it has not yet been set.

The return value is set when calling exit.

screen property

screen

The current active screen.

Returns:

Type	Description
Screen[object]	The currently active (visible) screen.

Raises:

Type	Description
ScreenStackError	If there are no screens on the stack.

screen_stack property

screen_stack

A snapshot of the current screen stack.

Returns:

Type	Description
Sequence[Screen[Any]]	A snapshot of the current state of the screen stack.

scroll_sensitivity_x instance-attribute

scroll_sensitivity_x = 4.0

Number of columns to scroll in the X direction with wheel or trackpad.

scroll_sensitivity_y instance-attribute

scroll_sensitivity_y = 2.0

Number of lines to scroll in the Y direction with wheel or trackpad.

size property

size

The size of the terminal.

Returns:

Type	Description
Size	Size of the terminal.

sub_title class-attribute instance-attribute

sub_title = SUB_TITLE if SUB_TITLE is not None else ''

The sub-title for the application.

The initial value for sub_title will be set to the SUB_TITLE class variable if it exists, or an empty string if it doesn't.

Sub-titles are typically used to show the high-level state of the app, such as the current mode, or path to the file being worked on.

Assign a new value to this attribute to change the sub-title. The new value is always converted to string.

title class-attribute instance-attribute

title = TITLE if TITLE is not None else f'{__name__}'

The title for the application.

The initial value for title will be set to the TITLE class variable if it exists, or the name of the app if it doesn't.

Assign a new value to this attribute to change the title. The new value is always converted to string.

use_command_palette instance-attribute

use_command_palette = ENABLE_COMMAND_PALETTE

A flag to say if the application should use the command palette.

If set to False any call to action_command_palette will be ignored.

workers property

workers

The worker manager.

Returns:

Type	Description
WorkerManager	An object to manage workers.

action_add_class async

action_add_class(selector, class_name)

An action to add a CSS class to the selected widget.

Parameters:

Name	Type	Description	Default
selector	str	Selects the widget to add the class to.	required
class_name	str	The class to add to the selected widget.	required

action_back async

action_back()

An action to go back to the previous screen (pop the current screen).

Note

If there is no screen to go back to, this is a non-operation (in other words it's safe to call even if there are no other screens on the stack.)

action_bell async

action_bell()

An action to play the terminal 'bell'.

action_command_palette

action_command_palette()

Show the Textual command palette.

action_focus async

action_focus(widget_id)

An action to focus the given widget.

Parameters:

Name	Type	Description	Default
widget_id	str	ID of widget to focus.	required

action_focus_next

action_focus_next()

An action to focus the next widget.

action_focus_previous

action_focus_previous()

An action to focus the previous widget.

action_pop_screen async

action_pop_screen()

An action to remove the topmost screen and makes the new topmost screen active.

action_push_screen async

action_push_screen(screen)

An action to push a new screen on to the stack and make it active.

Parameters:

Name	Type	Description	Default
screen	str	Name of the screen.	required

action_quit async

action_quit()

An action to quit the app as soon as possible.

action_remove_class async

action_remove_class(selector, class_name)

An action to remove a CSS class from the selected widget.

Parameters:

Name	Type	Description	Default
selector	str	Selects the widget to remove the class from.	required
class_name	str	The class to remove from the selected widget.	required

action_screenshot

action_screenshot(filename=None, path='./')

This action will save an SVG file containing the current contents of the screen.

Parameters:

Name	Type	Description	Default
filename	str | None	Filename of screenshot, or None to auto-generate.	None
path	str	Path to directory. Defaults to current working directory.	'./'

action_simulate_key async

action_simulate_key(key)

An action to simulate a key press.

This will invoke the same actions as if the user had pressed the key.

Parameters:

Name	Type	Description	Default
key	str	The key to process.	required

action_suspend_process

action_suspend_process()

Suspend the process into the background.

Note

On Unix and Unix-like systems a SIGTSTP is sent to the application's process. Currently on Windows and when running under Textual Web this is a non-operation.

action_switch_mode async

action_switch_mode(mode)

An action that switches to the given mode..

action_switch_screen async

action_switch_screen(screen)

An action to switch screens.

Parameters:

Name	Type	Description	Default
screen	str	Name of the screen.	required

action_toggle_class async

action_toggle_class(selector, class_name)

An action to toggle a CSS class on the selected widget.

Parameters:

Name	Type	Description	Default
selector	str	Selects the widget to toggle the class on.	required
class_name	str	The class to toggle on the selected widget.	required

action_toggle_dark

action_toggle_dark()

An action to toggle dark mode.

add_mode

add_mode(mode, base_screen)

Adds a mode and its corresponding base screen to the app.

Parameters:

Name	Type	Description	Default
mode	str	The new mode.	required
base_screen	str | Screen | Callable[[], Screen]	The base screen associated with the given mode.	required

Raises:

Type	Description
InvalidModeError	If the name of the mode is not valid/duplicated.

animate

animate(
    attribute,
    value,
    *,
    final_value=...,
    duration=None,
    speed=None,
    delay=0.0,
    easing=DEFAULT_EASING,
    on_complete=None,
    level="full"
)

Animate an attribute.

See the guide for how to use the animation system.

Parameters:

Name	Type	Description	Default
attribute	str	Name of the attribute to animate.	required
value	float | Animatable	The value to animate to.	required
final_value	object	The final value of the animation.	...
duration	float | None	The duration (in seconds) of the animation.	None
speed	float | None	The speed of the animation.	None
delay	float	A delay (in seconds) before the animation starts.	0.0
easing	EasingFunction | str	An easing method.	DEFAULT_EASING
on_complete	CallbackType | None	A callable to invoke when the animation is finished.	None
level	AnimationLevel	Minimum level required for the animation to take place (inclusive).	'full'

batch_update

batch_update()

A context manager to suspend all repaints until the end of the batch.

begin_capture_print

begin_capture_print(target, stdout=True, stderr=True)

Capture content that is printed (or written to stdout / stderr).

If printing is captured, the target will be sent an events.Print message.

Parameters:

Name	Type	Description	Default
target	MessageTarget	The widget where print content will be sent.	required
stdout	bool	Capture stdout.	True
stderr	bool	Capture stderr.	True

bell

bell()

Play the console 'bell'.

For terminals that support a bell, this typically makes a notification or error sound. Some terminals may make no sound or display a visual bell indicator, depending on configuration.

bind

bind(
    keys,
    action,
    *,
    description="",
    show=True,
    key_display=None
)

Bind a key to an action.

Parameters:

Name	Type	Description	Default
keys	str	A comma separated list of keys, i.e.	required
action	str	Action to bind to.	required
description	str	Short description of action.	''
show	bool	Show key in UI.	True
key_display	str | None	Replacement text for key, or None to use default.	None

call_from_thread

call_from_thread(callback, *args, **kwargs)

Run a callable from another thread, and return the result.

Like asyncio apps in general, Textual apps are not thread-safe. If you call methods or set attributes on Textual objects from a thread, you may get unpredictable results.

This method will ensure that your code runs within the correct context.

Tip

Consider using post_message which is also thread-safe.

Parameters:

Name	Type	Description	Default
callback	Callable[..., CallThreadReturnType | Awaitable[CallThreadReturnType]]	A callable to run.	required
*args	Any	Arguments to the callback.	()
**kwargs	Any	Keyword arguments for the callback.	{}

Raises:

Type	Description
RuntimeError	If the app isn't running or if this method is called from the same thread where the app is running.

Returns:

Type	Description
CallThreadReturnType	The result of the callback.

capture_mouse

capture_mouse(widget)

Send all mouse events to the given widget or disable mouse capture.

Parameters:

Name	Type	Description	Default
widget	Widget | None	If a widget, capture mouse event, or None to end mouse capture.	required

clear_notifications

clear_notifications()

Clear all the current notifications.

compose

compose()

Yield child widgets for a container.

This method should be implemented in a subclass.

copy_to_clipboard

copy_to_clipboard(text)

Copy text to the clipboard.

Note

This does not work on macOS Terminal, but will work on most other terminals.

Parameters:

Name	Type	Description	Default
text	str	Text you wish to copy to the clipboard.	required

end_capture_print

end_capture_print(target)

End capturing of prints.

Parameters:

Name	Type	Description	Default
target	MessageTarget	The widget that was capturing prints.	required

exit

exit(result=None, return_code=0, message=None)

Exit the app, and return the supplied result.

Parameters:

Name	Type	Description	Default
result	ReturnType | None	Return value.	None
return_code	int	The return code. Use non-zero values for error codes.	0
message	RenderableType | None	Optional message to display on exit.	None

export_screenshot

export_screenshot(*, title=None)

Export an SVG screenshot of the current screen.

See also save_screenshot which writes the screenshot to a file.

Parameters:

Name	Type	Description	Default
title	str | None	The title of the exported screenshot or None to use app title.	None

get_child_by_id

get_child_by_id(id: str) -> Widget

get_child_by_id(
    id: str, expect_type: type[ExpectType]
) -> ExpectType

get_child_by_id(id, expect_type=None)

Get the first child (immediate descendant) of this DOMNode with the given ID.

Parameters:

Name	Type	Description	Default
id	str	The ID of the node to search for.	required
expect_type	type[ExpectType] | None	Require the object be of the supplied type, or use None to apply no type restriction.	None

Returns:

Type	Description
ExpectType | Widget	The first child of this node with the specified ID.

Raises:

Type	Description
NoMatches	If no children could be found for this ID.
WrongType	If the wrong type was found.

get_child_by_type

get_child_by_type(expect_type)

Get a child of a give type.

Parameters:

Name	Type	Description	Default
expect_type	type[ExpectType]	The type of the expected child.	required

Raises:

Type	Description
NoMatches	If no valid child is found.

Returns:

Type	Description
ExpectType	A widget.

get_css_variables

get_css_variables()

Get a mapping of variables used to pre-populate CSS.

May be implemented in a subclass to add new CSS variables.

Returns:

Type	Description
dict[str, str]	A mapping of variable name to value.

get_default_screen

get_default_screen()

Get the default screen.

This is called when the App is first composed. The returned screen instance will be the first screen on the stack.

Implement this method if you would like to use a custom Screen as the default screen.

Returns:

Type	Description
Screen	A screen instance.

get_driver_class

get_driver_class()

Get a driver class for this platform.

This method is called by the constructor, and unlikely to be required when building a Textual app.

Returns:

Type	Description
Type[Driver]	A Driver class which manages input and display.

get_key_display

get_key_display(key)

For a given key, return how it should be displayed in an app (e.g. in the Footer widget). By key, we refer to the string used in the "key" argument for a Binding instance. By overriding this method, you can ensure that keys are displayed consistently throughout your app, without needing to add a key_display to every binding.

Parameters:

Name	Type	Description	Default
key	str	The binding key string.	required

Returns:

Type	Description
str	The display string for the input key.

get_loading_widget

get_loading_widget()

Get a widget to be used as a loading indicator.

Extend this method if you want to display the loading state a little differently.

Returns:

Type	Description
Widget	A widget to display a loading state.

get_screen

get_screen(screen)

Get an installed screen.

Parameters:

Name	Type	Description	Default
screen	Screen | str	Either a Screen object or screen name (the name argument when installed).	required

Raises:

Type	Description
KeyError	If the named screen doesn't exist.

Returns:

Type	Description
Screen	A screen instance.

get_widget_at

get_widget_at(x, y)

Get the widget under the given coordinates.

Parameters:

Name	Type	Description	Default
x	int	X coordinate.	required
y	int	Y coordinate.	required

Returns:

Type	Description
tuple[Widget, Region]	The widget and the widget's screen region.

get_widget_by_id

get_widget_by_id(id: str) -> Widget

get_widget_by_id(
    id: str, expect_type: type[ExpectType]
) -> ExpectType

get_widget_by_id(id, expect_type=None)

Get the first descendant widget with the given ID.

Performs a breadth-first search rooted at the current screen. It will not return the Screen if that matches the ID. To get the screen, use self.screen.

Parameters:

Name	Type	Description	Default
id	str	The ID to search for in the subtree	required
expect_type	type[ExpectType] | None	Require the object be of the supplied type, or None for any type. Defaults to None.	None

Returns:

Type	Description
ExpectType | Widget	The first descendant encountered with this ID.

Raises:

Type	Description
NoMatches	if no children could be found for this ID
WrongType	if the wrong type was found.

install_screen

install_screen(screen, name)

Install a screen.

Installing a screen prevents Textual from destroying it when it is no longer on the screen stack. Note that you don't need to install a screen to use it. See push_screen or switch_screen to make a new screen current.

Parameters:

Name	Type	Description	Default
screen	Screen	Screen to install.	required
name	str	Unique name to identify the screen.	required

Raises:

Type	Description
ScreenError	If the screen can't be installed.

Returns:

Type	Description
None	An awaitable that awaits the mounting of the screen and its children.

is_mounted

is_mounted(widget)

Check if a widget is mounted.

Parameters:

Name	Type	Description	Default
widget	Widget	A widget.	required

Returns:

Type	Description
bool	True of the widget is mounted.

is_screen_installed

is_screen_installed(screen)

Check if a given screen has been installed.

Parameters:

Name	Type	Description	Default
screen	Screen | str	Either a Screen object or screen name (the name argument when installed).	required

Returns:

Type	Description
bool	True if the screen is currently installed,

mount

mount(*widgets, before=None, after=None)

Mount the given widgets relative to the app's screen.

Parameters:

Name	Type	Description	Default
*widgets	Widget	The widget(s) to mount.	()
before	int | str | Widget | None	Optional location to mount before. An int is the index of the child to mount before, a str is a query_one query to find the widget to mount before.	None
after	int | str | Widget | None	Optional location to mount after. An int is the index of the child to mount after, a str is a query_one query to find the widget to mount after.	None

Returns:

Type	Description
AwaitMount	An awaitable object that waits for widgets to be mounted.

Raises:

Type	Description
MountError	If there is a problem with the mount request.

Note

Only one of before or after can be provided. If both are provided a MountError will be raised.

mount_all

mount_all(widgets, *, before=None, after=None)

Mount widgets from an iterable.

Parameters:

Name	Type	Description	Default
widgets	Iterable[Widget]	An iterable of widgets.	required
before	int | str | Widget | None	Optional location to mount before. An int is the index of the child to mount before, a str is a query_one query to find the widget to mount before.	None
after	int | str | Widget | None	Optional location to mount after. An int is the index of the child to mount after, a str is a query_one query to find the widget to mount after.	None

Returns:

Type	Description
AwaitMount	An awaitable object that waits for widgets to be mounted.

Raises:

Type	Description
MountError	If there is a problem with the mount request.

Note

Only one of before or after can be provided. If both are provided a MountError will be raised.

notify

notify(
    message,
    *,
    title="",
    severity="information",
    timeout=None
)

Create a notification.

Tip

This method is thread-safe.

Parameters:

Name	Type	Description	Default
message	str	The message for the notification.	required
title	str	The title for the notification.	''
severity	SeverityLevel	The severity of the notification.	'information'
timeout	float | None	The timeout (in seconds) for the notification, or None for default.	None

The notify method is used to create an application-wide notification, shown in a Toast, normally originating in the bottom right corner of the display.

Notifications can have the following severity levels:

• information
• warning
• error

The default is information.

Example

# Show an information notification.
self.notify("It's an older code, sir, but it checks out.")

# Show a warning. Note that Textual's notification system allows
# for the use of Rich console markup.
self.notify(
    "Now witness the firepower of this fully "
    "[b]ARMED[/b] and [i][b]OPERATIONAL[/b][/i] battle station!",
    title="Possible trap detected",
    severity="warning",
)

# Show an error. Set a longer timeout so it's noticed.
self.notify("It's a trap!", severity="error", timeout=10)

# Show an information notification, but without any sort of title.
self.notify("It's against my programming to impersonate a deity.", title="")

panic

panic(*renderables)

Exits the app and display error message(s).

Used in response to unexpected errors. For a more graceful exit, see the exit method.

Parameters:

Name	Type	Description	Default
*renderables	RenderableType	Text or Rich renderable(s) to display on exit.	()

pop_screen

pop_screen()

Pop the current screen from the stack, and switch to the previous screen.

Returns:

Type	Description
AwaitComplete	The screen that was replaced.

post_display_hook

post_display_hook()

Called immediately after a display is done. Used in tests.

push_screen

push_screen(
    screen: Screen[ScreenResultType] | str,
    callback: (
        ScreenResultCallbackType[ScreenResultType] | None
    ) = None,
    wait_for_dismiss: Literal[False] = False,
) -> AwaitMount

push_screen(
    screen: Screen[ScreenResultType] | str,
    callback: (
        ScreenResultCallbackType[ScreenResultType] | None
    ) = None,
    wait_for_dismiss: Literal[True] = True,
) -> Future[ScreenResultType]

push_screen(screen, callback=None, wait_for_dismiss=False)

Push a new screen on the screen stack, making it the current screen.

Parameters:

Name	Type	Description	Default
screen	Screen[ScreenResultType] | str	A Screen instance or the name of an installed screen.	required
callback	ScreenResultCallbackType[ScreenResultType] | None	An optional callback function that will be called if the screen is dismissed with a result.	None
wait_for_dismiss	bool	If True, awaiting this method will return the dismiss value from the screen. When set to False, awaiting this method will wait for the screen to be mounted. Note that wait_for_dismiss should only be set to True when running in a worker.	False

Raises:

Type	Description
NoActiveWorker	If using wait_for_dismiss outside of a worker.

Returns:

Type	Description
AwaitMount | Future[ScreenResultType]	An optional awaitable that awaits the mounting of the screen and its children, or an asyncio Future to await the result of the screen.

push_screen_wait async

push_screen_wait(
    screen: Screen[ScreenResultType],
) -> ScreenResultType

push_screen_wait(screen: str) -> Any

push_screen_wait(screen)

Push a screen and wait for the result (received from Screen.dismiss).

Note that this method may only be called when running in a worker.

Parameters:

Name	Type	Description	Default
screen	Screen[ScreenResultType] | str	A screen or the name of an installed screen.	required

Returns:

Type	Description
ScreenResultType | Any	The screen's result.

recompose async

recompose()

Recompose the widget.

Recomposing will remove children and call self.compose again to remount.

refresh

refresh(*, repaint=True, layout=False, recompose=False)

Refresh the entire screen.

Parameters:

Name	Type	Description	Default
repaint	bool	Repaint the widget (will call render() again).	True
layout	bool	Also layout widgets in the view.	False
recompose	bool	Re-compose the widget (will remove and re-mount children).	False

Returns:

Type	Description
Self	The App instance.

refresh_css

refresh_css(animate=True)

Refresh CSS.

Parameters:

Name	Type	Description	Default
animate	bool	Also execute CSS animations.	True

remove_mode

remove_mode(mode)

Removes a mode from the app.

Screens that are running in the stack of that mode are scheduled for pruning.

Parameters:

Name	Type	Description	Default
mode	str	The mode to remove. It can't be the active mode.	required

Raises:

Type	Description
ActiveModeError	If trying to remove the active mode.
UnknownModeError	If trying to remove an unknown mode.

render

render()

Render method, inherited from widget, to render the screen's background.

May be overridden to customize background visuals.

run

run(
    *,
    headless=False,
    inline=False,
    inline_no_clear=False,
    mouse=True,
    size=None,
    auto_pilot=None
)

Run the app.

Parameters:

Name	Type	Description	Default
headless	bool	Run in headless mode (no output).	False
inline	bool	Run the app inline (under the prompt).	False
inline_no_clear	bool	Don't clear the app output when exiting an inline app.	False
mouse	bool	Enable mouse support.	True
size	tuple[int, int] | None	Force terminal size to (WIDTH, HEIGHT), or None to auto-detect.	None
auto_pilot	AutopilotCallbackType | None	An auto pilot coroutine.	None

Returns:

Type	Description
ReturnType | None	App return value.

run_action async

run_action(action, default_namespace=None)

Perform an action.

Actions are typically associated with key bindings, where you wouldn't need to call this method manually.

Parameters:

Name	Type	Description	Default
action	str | ActionParseResult	Action encoded in a string.	required
default_namespace	DOMNode | None	Namespace to use if not provided in the action, or None to use app.	None

Returns:

Type	Description
bool	True if the event has been handled.

run_async async

run_async(
    *,
    headless=False,
    inline=False,
    inline_no_clear=False,
    mouse=True,
    size=None,
    auto_pilot=None
)

Run the app asynchronously.

Parameters:

Name	Type	Description	Default
headless	bool	Run in headless mode (no output).	False
inline	bool	Run the app inline (under the prompt).	False
inline_no_clear	bool	Don't clear the app output when exiting an inline app.	False
mouse	bool	Enable mouse support.	True
size	tuple[int, int] | None	Force terminal size to (WIDTH, HEIGHT), or None to auto-detect.	None
auto_pilot	AutopilotCallbackType | None	An autopilot coroutine.	None

Returns:

Type	Description
ReturnType | None	App return value.

run_test async

run_test(
    *,
    headless=True,
    size=(80, 24),
    tooltips=False,
    notifications=False,
    message_hook=None
)

An asynchronous context manager for testing apps.

Tip

See the guide for testing Textual apps.

Use this to run your app in "headless" mode (no output) and drive the app via a Pilot object.

Example:

```python
async with app.run_test() as pilot:
    await pilot.click("#Button.ok")
    assert ...
```

Parameters:

Name	Type	Description	Default
headless	bool	Run in headless mode (no output or input).	True
size	tuple[int, int] | None	Force terminal size to (WIDTH, HEIGHT), or None to auto-detect.	(80, 24)
tooltips	bool	Enable tooltips when testing.	False
notifications	bool	Enable notifications when testing.	False
message_hook	Callable[[Message], None] | None	An optional callback that will be called each time any message arrives at any message pump in the app.	None

save_screenshot

save_screenshot(filename=None, path=None, time_format=None)

Save an SVG screenshot of the current screen.

Parameters:

Name	Type	Description	Default
filename	str | None	Filename of SVG screenshot, or None to auto-generate a filename with the date and time.	None
path	str | None	Path to directory for output. Defaults to current working directory.	None
time_format	str | None	Date and time format to use if filename is None. Defaults to a format like ISO 8601 with some reserved characters replaced with underscores.	None

Returns:

Type	Description
str	Filename of screenshot.

set_focus

set_focus(widget, scroll_visible=True)

Focus (or unfocus) a widget. A focused widget will receive key events first.

Parameters:

Name	Type	Description	Default
widget	Widget | None	Widget to focus.	required
scroll_visible	bool	Scroll widget in to view.	True

simulate_key

simulate_key(key)

Simulate a key press.

This will perform the same action as if the user had pressed the key.

Parameters:

Name	Type	Description	Default
key	str	Key to simulate. May also be the name of a key, e.g. "space".	required

stop_animation async

stop_animation(attribute, complete=True)

Stop an animation on an attribute.

Parameters:

Name	Type	Description	Default
attribute	str	Name of the attribute whose animation should be stopped.	required
complete	bool	Should the animation be set to its final value?	True

Note

If there is no animation scheduled or running, this is a no-op.

suspend

suspend()

A context manager that temporarily suspends the app.

While inside the with block, the app will stop reading input and emitting output. Other applications will have full control of the terminal, configured as it was before the app started running. When the with block ends, the application will start reading input and emitting output again.

Example

with self.suspend():
    os.system("emacs -nw")

Raises:

Type	Description
SuspendNotSupported	If the environment doesn't support suspending.

Note

Suspending the application is currently only supported on Unix-like operating systems and Microsoft Windows. Suspending is not supported in Textual Web.

switch_mode

switch_mode(mode)

Switch to a given mode.

Parameters:

Name	Type	Description	Default
mode	str	The mode to switch to.	required

Returns:

Type	Description
AwaitMount	An optionally awaitable object which waits for the screen associated with the mode to be mounted.

Raises:

Type	Description
UnknownModeError	If trying to switch to an unknown mode.

switch_screen

switch_screen(screen)

Switch to another screen by replacing the top of the screen stack with a new screen.

Parameters:

Name	Type	Description	Default
screen	Screen | str	Either a Screen object or screen name (the name argument when installed).	required

uninstall_screen

uninstall_screen(screen)

Uninstall a screen.

If the screen was not previously installed, then this method is a null-op. Uninstalling a screen allows Textual to delete it when it is popped or switched. Note that uninstalling a screen is only required if you have previously installed it with install_screen. Textual will also uninstall screens automatically on exit.

Parameters:

Name	Type	Description	Default
screen	Screen | str	The screen to uninstall or the name of an installed screen.	required

Returns:

Type	Description
str | None	The name of the screen that was uninstalled, or None if no screen was uninstalled.

update_styles

update_styles(node)

Immediately update the styles of this node and all descendant nodes.

Should be called whenever CSS classes / pseudo classes change. For example, when you hover over a button, the :hover pseudo class will be added, and this method is called to apply the corresponding :hover styles.

validate_sub_title

validate_sub_title(sub_title)

Make sure the subtitle is set to a string.

validate_title

validate_title(title)

Make sure the title is set to a string.

watch_dark

watch_dark(dark)

Watches the dark bool.

This method handles the transition between light and dark mode when you change the dark attribute.

AppError

Bases: Exception

Base class for general App related exceptions.

InvalidModeError

Bases: ModeError

Raised if there is an issue with a mode name.

ModeError

Bases: Exception

Base class for exceptions related to modes.

ScreenError

Bases: Exception

Base class for exceptions that relate to screens.

ScreenStackError

Bases: ScreenError

Raised when trying to manipulate the screen stack incorrectly.

SuspendNotSupported

Bases: Exception

Raised if suspending the application is not supported.

This exception is raised if App.suspend is called while the application is running in an environment where this isn't supported.

UnknownModeError

Bases: ModeError

Raised when attempting to use a mode that is not known.

get_system_commands

get_system_commands()

Callable to lazy load the system commands.

Returns:

Type	Description
type[SystemCommands]	System commands class.