textual.dom

The module contains DOMNode, the base class for any object within the Textual Document Object Model, which includes all Widgets, Screens, and Apps.

WalkMethod `module-attribute` ¶

WalkMethod = Literal['depth', 'breadth']

Valid walking methods for the DOMNode.walk_children method.

BadIdentifier ¶

Bases: Exception

Exception raised if you supply a id attribute or class name in the wrong format.

DOMError ¶

Bases: Exception

Base exception class for errors relating to the DOM.

DOMNode ¶

DOMNode(*, name=None, id=None, classes=None)

Bases: MessagePump

The base class for object that can be in the Textual DOM (App and Widget)

SCOPED_CSS `class-attribute` ¶

SCOPED_CSS = True

Should default css be limited to the widget type?

ancestors `property` ¶

ancestors

A list of ancestor nodes found by tracing a path all the way back to App.

Returns:

Type	Description
`list[DOMNode]`	A list of nodes.

ancestors_with_self `property` ¶

ancestors_with_self

A list of ancestor nodes found by tracing a path all the way back to App.

Note

This is inclusive of self.

Returns:

Type	Description
`list[DOMNode]`	A list of nodes.

auto_refresh `property` `writable` ¶

auto_refresh

Number of seconds between automatic refresh, or None for no automatic refresh.

background_colors `property` ¶

background_colors

The background color and the color of the parent's background.

Returns:

Type	Description
`tuple[Color, Color]`	`(<background color>, <color>)`

children `property` ¶

children

A view on to the children.

Returns:

Type	Description
`Sequence['Widget']`	The node's children.

classes `class-attribute` `instance-attribute` ¶

classes = _ClassesDescriptor()

CSS class names for this node.

colors `property` ¶

colors

The widget's background and foreground colors, and the parent's background and foreground colors.

Returns:

Type	Description
`tuple[Color, Color, Color, Color]`	`(<parent background>, <parent color>, <background>, <color>)`

css_identifier `property` ¶

css_identifier

A CSS selector that identifies this DOM node.

css_identifier_styled `property` ¶

css_identifier_styled

A syntax highlighted CSS identifier.

Returns:

Type	Description
`Text`	A Rich Text object.

css_path_nodes `property` ¶

css_path_nodes

A list of nodes from the App to this node, forming a "path".

Returns:

Type	Description
`list[DOMNode]`	A list of nodes, where the first item is the App, and the last is this node.

css_tree `property` ¶

css_tree

A Rich tree to display the DOM, annotated with the node's CSS.

Log this to visualize your app in the textual console.

Example

self.log(self.css_tree)

Returns:

Type	Description
`Tree`	A Tree renderable.

display `property` `writable` ¶

display

Should the DOM node be displayed?

May be set to a boolean to show or hide the node, or to any valid value for the display rule.

Example

my_widget.display = False  # Hide my_widget

displayed_children `property` ¶

displayed_children

The child nodes which will be displayed.

Returns:

Type	Description
`list[Widget]`	A list of nodes.

id `property` `writable` ¶

id

The ID of this node, or None if the node has no ID.

is_modal `property` ¶

is_modal

Is the node a modal?

name `property` ¶

name

The name of the node.

parent `property` ¶

parent

The parent node.

All nodes have parent once added to the DOM, with the exception of the App which is the root node.

pseudo_classes `property` ¶

pseudo_classes

A (frozen) set of all pseudo classes.

rich_style `property` ¶

rich_style

Get a Rich Style object for this DOMNode.

Returns:

Type	Description
`Style`	A Rich style.

screen `property` ¶

screen

The screen containing this node.

Returns:

Type	Description
`'Screen[object]'`	A screen object.

Raises:

Type	Description
`NoScreen`	If this node isn't mounted (and has no screen).

text_style `property` ¶

text_style

Get the text style object.

A widget's style is influenced by its parent. for instance if a parent is bold, then the child will also be bold.

Returns:

Type	Description
`Style`	A Rich Style.

tree `property` ¶

tree

A Rich tree to display the DOM.

Log this to visualize your app in the textual console.

Example

self.log(self.tree)

Returns:

Type	Description
`Tree`	A Tree renderable.

visible `property` `writable` ¶

visible

Is this widget visible in the DOM?

If a widget hasn't had its visibility set explicitly, then it inherits it from its DOM ancestors.

This may be set explicitly to override inherited values. The valid values include the valid values for the visibility rule and the booleans True or False, to set the widget to be visible or invisible, respectively.

When a node is invisible, Textual will reserve space for it, but won't display anything.

workers `property` ¶

workers

The app's worker manager. Shortcut for self.app.workers.

action_toggle `async` ¶

action_toggle(attribute_name)

Toggle an attribute on the node.

Assumes the attribute is a bool.

Parameters:

Name	Type	Description	Default
`attribute_name` ¶	`str`	Name of the attribute.	required

add_class ¶

add_class(*class_names, update=True)

Add class names to this Node.

Parameters:

Name	Type	Description	Default
`*class_names` ¶	`str`	CSS class names to add.	`()`
`update` ¶	`bool`	Also update styles.	`True`

Returns:

Type	Description
`Self`	Self.

check_action ¶

check_action(action, parameters)

Check whether an action is enabled.

Implement this method to add logic for dynamic actions / bindings.

Parameters:

Name	Type	Description	Default
`action` ¶	`str`	The name of an action.	required
`action_parameters` ¶		A tuple of any action parameters.	required

Returns:

Type	Description
`bool \| None`	`True` if the action is enabled+visible, `False` if the action is disabled+hidden, `None` if the action is disabled+visible (grayed out in footer)

data_bind ¶

data_bind(*reactives, **bind_vars)

Bind reactive data so that changes to a reactive automatically change the reactive on another widget.

Reactives may be given as positional arguments or keyword arguments. See the guide on data binding.

Example

def compose(self) -> ComposeResult:
    yield WorldClock("Europe/London").data_bind(WorldClockApp.time)
    yield WorldClock("Europe/Paris").data_bind(WorldClockApp.time)
    yield WorldClock("Asia/Tokyo").data_bind(WorldClockApp.time)

Raises:

Type	Description
`ReactiveError`	If the data wasn't bound.

Returns:

Type	Description
`Self`	Self.

get_component_styles ¶

get_component_styles(*names)

Get a "component" styles object (must be defined in COMPONENT_CLASSES classvar).

Parameters:

Name	Type	Description	Default
`name` ¶		Name of the component.	required

Raises:

Type	Description
`KeyError`	If the component class doesn't exist.

Returns:

Type	Description
`RenderStyles`	A Styles object.

get_pseudo_classes ¶

get_pseudo_classes()

Get any pseudo classes applicable to this Node, e.g. hover, focus.

Returns:

Type	Description
`Iterable[str]`	Iterable of strings, such as a generator.

has_class ¶

has_class(*class_names)

Check if the Node has all the given class names.

Parameters:

Name	Type	Description	Default
`*class_names` ¶	`str`	CSS class names to check.	`()`

Returns:

Type	Description
`bool`	`True` if the node has all the given class names, otherwise `False`.

has_pseudo_class ¶

has_pseudo_class(class_name)

Check the node has the given pseudo class.

Parameters:

Name	Type	Description	Default
`class_name` ¶	`str`	The pseudo class to check for.	required

Returns:

Type	Description
`bool`	`True` if the DOM node has the pseudo class, `False` if not.

has_pseudo_classes ¶

has_pseudo_classes(class_names)

Check the node has all the given pseudo classes.

Parameters:

Name	Type	Description	Default
`class_names` ¶	`set[str]`	Set of class names to check for.	required

Returns:

Type	Description
`bool`	`True` if all pseudo class names are present.

mutate_reactive ¶

mutate_reactive(reactive)

Force an update to a mutable reactive.

Example

self.reactive_name_list.append("Jessica")
self.mutate_reactive(MyClass.reactive_name_list)

Textual will automatically detect when a reactive is set to a new value, but it is unable to detect if a value is mutated (such as updating a list, dict, or attribute of an object). If you do wish to use a collection or other mutable object in a reactive, then you can call this method after your reactive is updated. This will ensure that all the reactive superpowers work.

Parameters:

Name	Type	Description	Default
`reactive` ¶	`Reactive[ReactiveType]`	A reactive property (use the class scope syntax, i.e. `MyClass.my_reactive`).	required

notify_style_update ¶

notify_style_update()

Called after styles are updated.

Implement this in a subclass if you want to clear any cached data when the CSS is reloaded.

query ¶

query(selector: str | None = None) -> DOMQuery[Widget]

query(selector: type[QueryType]) -> DOMQuery[QueryType]

query(selector=None)

Query the DOM for children that match a selector or widget type.

Parameters:

Name	Type	Description	Default
`selector` ¶	`str \| type[QueryType] \| None`	A CSS selector, widget type, or `None` for all nodes.	`None`

Returns:

Type	Description
`DOMQuery[Widget] \| DOMQuery[QueryType]`	A query object.

query_children ¶

query_children(
    selector: str | None = None,
) -> DOMQuery[Widget]

query_children(
    selector: type[QueryType],
) -> DOMQuery[QueryType]

query_children(selector=None)

Query the DOM for the immediate children that match a selector or widget type.

Note that this will not return child widgets more than a single level deep. If you want to a query to potentially match all children in the widget tree, see query.

Parameters:

Name	Type	Description	Default
`selector` ¶	`str \| type[QueryType] \| None`	A CSS selector, widget type, or `None` for all nodes.	`None`

Returns:

Type	Description
`DOMQuery[Widget] \| DOMQuery[QueryType]`	A query object.

query_one ¶

query_one(selector: str) -> Widget

query_one(selector: type[QueryType]) -> QueryType

query_one(
    selector: str, expect_type: type[QueryType]
) -> QueryType

query_one(selector, expect_type=None)

Get a widget from this widget's children that matches a selector or widget type.

Parameters:

Name	Type	Description	Default
`selector` ¶	`str \| type[QueryType]`	A selector or widget type.	required
`expect_type` ¶	`type[QueryType] \| None`	Require the object be of the supplied type, or None for any type.	`None`

Raises:

Type	Description
`WrongType`	If the wrong type was found.
`NoMatches`	If no node matches the query.
`TooManyMatches`	If there is more than one matching node in the query.

Returns:

Type	Description
`QueryType \| Widget`	A widget matching the selector.

refresh_bindings ¶

refresh_bindings()

Call to prompt widgets such as the Footer to update the display of key bindings.

See actions for how to use this method.

remove_class ¶

remove_class(*class_names, update=True)

Remove class names from this Node.

Parameters:

Name	Type	Description	Default
`*class_names` ¶	`str`	CSS class names to remove.	`()`
`update` ¶	`bool`	Also update styles.	`True`

Returns:

Type	Description
`Self`	Self.

reset_styles ¶

reset_styles()

Reset styles back to their initial state.

run_worker ¶

run_worker(
    work,
    name="",
    group="default",
    description="",
    exit_on_error=True,
    start=True,
    exclusive=False,
    thread=False,
)

Run work in a worker.

A worker runs a function, coroutine, or awaitable, in the background as an async task or as a thread.

Parameters:

Name	Type	Description	Default
`work` ¶	`WorkType[ResultType]`	A function, async function, or an awaitable object to run in a worker.	required
`name` ¶	`str \| None`	A short string to identify the worker (in logs and debugging).	`''`
`group` ¶	`str`	A short string to identify a group of workers.	`'default'`
`description` ¶	`str`	A longer string to store longer information on the worker.	`''`
`exit_on_error` ¶	`bool`	Exit the app if the worker raises an error. Set to `False` to suppress exceptions.	`True`
`start` ¶	`bool`	Start the worker immediately.	`True`
`exclusive` ¶	`bool`	Cancel all workers in the same group.	`False`
`thread` ¶	`bool`	Mark the worker as a thread worker.	`False`

Returns:

Type	Description
`Worker[ResultType]`	New Worker instance.

set_class ¶

set_class(add, *class_names, update=True)

Add or remove class(es) based on a condition.

Parameters:

Name	Type	Description	Default
`add` ¶	`bool`	Add the classes if True, otherwise remove them.	required
`update` ¶	`bool`	Also update styles.	`True`

Returns:

Type	Description
`Self`	Self.

set_classes ¶

set_classes(classes)

Replace all classes.

Parameters:

Name	Type	Description	Default
`classes` ¶	`str \| Iterable[str]`	A string containing space separated classes, or an iterable of class names.	required

Returns:

Type	Description
`Self`	Self.

set_reactive ¶

set_reactive(reactive, value)

Sets a reactive value without invoking validators or watchers.

Example

self.set_reactive(App.dark_mode, True)

Parameters:

Name	Type	Description	Default
`reactive` ¶	`Reactive[ReactiveType]`	A reactive property (use the class scope syntax, i.e. `MyClass.my_reactive`).	required
`value` ¶	`ReactiveType`	New value of reactive.	required

Raises:

Type	Description
`AttributeError`	If the first argument is not a reactive.

set_styles ¶

set_styles(css=None, **update_styles)

Set custom styles on this object.

Parameters:

Name	Type	Description	Default
`css` ¶	`str \| None`	Styles in CSS format.	`None`
`update_styles` ¶	`Any`	Keyword arguments map style names onto style values.	`{}`

Returns:

Type	Description
`Self`	Self.

sort_children ¶

sort_children(*, key=None, reverse=False)

Sort child widgets with an optional key function.

If key is not provided then widgets will be sorted in the order they are constructed.

Example

# Sort widgets by name
screen.sort_children(key=lambda widget: widget.name or "")

Parameters:

Name	Type	Description	Default
`key` ¶	`Callable[[Widget], SupportsRichComparison] \| None`	A callable which accepts a widget and returns something that can be sorted, or `None` to sort without a key function.	`None`
`reverse` ¶	`bool`	Sort in descending order.	`False`

toggle_class ¶

toggle_class(*class_names)

Toggle class names on this Node.

Parameters:

Name	Type	Description	Default
`*class_names` ¶	`str`	CSS class names to toggle.	`()`

Returns:

Type	Description
`Self`	Self.

walk_children ¶

walk_children(
    filter_type: type[WalkType],
    *,
    with_self: bool = False,
    method: WalkMethod = "depth",
    reverse: bool = False
) -> list[WalkType]

walk_children(
    *,
    with_self: bool = False,
    method: WalkMethod = "depth",
    reverse: bool = False
) -> list[DOMNode]

walk_children(
    filter_type=None,
    *,
    with_self=False,
    method="depth",
    reverse=False
)

Walk the subtree rooted at this node, and return every descendant encountered in a list.

Parameters:

Name	Type	Description	Default
`filter_type` ¶	`type[WalkType] \| None`	Filter only this type, or None for no filter.	`None`
`with_self` ¶	`bool`	Also yield self in addition to descendants.	`False`
`method` ¶	`WalkMethod`	One of "depth" or "breadth".	`'depth'`
`reverse` ¶	`bool`	Reverse the order (bottom up).	`False`

Returns:

Type	Description
`list[DOMNode] \| list[WalkType]`	A list of nodes.

watch ¶

watch(obj, attribute_name, callback, init=True)

Watches for modifications to reactive attributes on another object.

Example:

Here's how you could detect when the app changes from dark to light mode (and vice versa).

```python
def on_dark_change(old_value:bool, new_value:bool):
    # Called when app.dark changes.
    print("App.dark when from {old_value} to {new_value}")

self.watch(self.app, "dark", self.on_dark_change, init=False)
```

Parameters:

Name	Type	Description	Default
`obj` ¶	`DOMNode`	Object containing attribute to watch.	required
`attribute_name` ¶	`str`	Attribute to watch.	required
`callback` ¶	`WatchCallbackType`	A callback to run when attribute changes.	required
`init` ¶	`bool`	Check watchers on first call.	`True`

NoScreen ¶

Bases: DOMError

Raised when the node has no associated screen.

check_identifiers ¶

check_identifiers(description, *names)

Validate identifier and raise an error if it fails.

Parameters:

Name	Type	Description	Default
`description` ¶	`str`	Description of where identifier is used for error message.	required
`*names` ¶	`str`	Identifiers to check.	`()`

textual.dom

WalkMethod module-attribute ¶

BadIdentifier ¶

DOMError ¶

DOMNode ¶

SCOPED_CSS class-attribute ¶

ancestors property ¶

ancestors_with_self property ¶

auto_refresh property writable ¶

background_colors property ¶

children property ¶

classes class-attribute instance-attribute ¶

colors property ¶

css_identifier property ¶

css_identifier_styled property ¶

css_path_nodes property ¶

css_tree property ¶

display property writable ¶

displayed_children property ¶

id property writable ¶

is_modal property ¶

name property ¶

parent property ¶

pseudo_classes property ¶

rich_style property ¶

screen property ¶

text_style property ¶

tree property ¶

visible property writable ¶

workers property ¶

action_toggle async ¶

attribute_name ¶

add_class ¶

*class_names ¶

update ¶

check_action ¶

action ¶

action_parameters ¶

data_bind ¶

get_component_styles ¶

name ¶

get_pseudo_classes ¶

has_class ¶

*class_names ¶

has_pseudo_class ¶

class_name ¶

has_pseudo_classes ¶

class_names ¶

mutate_reactive ¶

reactive ¶

notify_style_update ¶

query ¶

selector ¶

query_children ¶

selector ¶

query_one ¶

selector ¶

expect_type ¶

refresh_bindings ¶

remove_class ¶

*class_names ¶

update ¶

reset_styles ¶

run_worker ¶

work ¶

name ¶

group ¶

description ¶

exit_on_error ¶

start ¶

exclusive ¶

thread ¶

set_class ¶

add ¶

update ¶

set_classes ¶

classes ¶

set_reactive ¶

reactive ¶

value ¶

WalkMethod `module-attribute` ¶

SCOPED_CSS `class-attribute` ¶

ancestors `property` ¶

ancestors_with_self `property` ¶

auto_refresh `property` `writable` ¶

background_colors `property` ¶

children `property` ¶

classes `class-attribute` `instance-attribute` ¶

colors `property` ¶

css_identifier `property` ¶

css_identifier_styled `property` ¶

css_path_nodes `property` ¶

css_tree `property` ¶

display `property` `writable` ¶

displayed_children `property` ¶

id `property` `writable` ¶

is_modal `property` ¶

name `property` ¶

parent `property` ¶

pseudo_classes `property` ¶

rich_style `property` ¶

screen `property` ¶

text_style `property` ¶

tree `property` ¶

visible `property` `writable` ¶

workers `property` ¶

action_toggle `async` ¶

`attribute_name` ¶

`*class_names` ¶

`update` ¶

`action` ¶

`action_parameters` ¶

`name` ¶

`*class_names` ¶

`class_name` ¶

`class_names` ¶

`reactive` ¶

`selector` ¶

`selector` ¶

`selector` ¶

`expect_type` ¶

`*class_names` ¶

`update` ¶

`work` ¶

`name` ¶

`group` ¶

`description` ¶

`exit_on_error` ¶

`start` ¶

`exclusive` ¶

`thread` ¶

`add` ¶

`update` ¶

`classes` ¶

`reactive` ¶

`value` ¶

`css` ¶

`update_styles` ¶

`key` ¶

`reverse` ¶

`*class_names` ¶

`filter_type` ¶

`with_self` ¶

`method` ¶

`reverse` ¶

`obj` ¶

`attribute_name` ¶

`callback` ¶

`init` ¶

`description` ¶

`*names` ¶