bootstack.Select#

class bootstack.Select(options=None, *, value=None, signal=None, label=None, message=None, required=False, searchable=False, allow_custom_values=False, group_by=None, max_visible_items=None, read_only=False, disabled=False, width=None, accent=None, density=None, localize=None, parent=None, **kwargs)#

Bases: ValueSignalMixin, FieldAddonMixin, PublicWidgetBase

A single-selection dropdown field.

The options list is the first positional argument. All options are keyword-only.

Parameters:

options (list[Option] | None) – Choices presented in the popup. Each item is a plain string, a (text, value) tuple, or a {'text': ..., 'value': ...} dict — so an option’s displayed label can differ from its stored value. A dict option may also carry 'icon' (a glyph rendered beside the row label) and 'disabled' (when True the row is dimmed and cannot be chosen); any other keys ride along as carried data on selection. Defaults to an empty list.
value (Any) – Initially selected value (value-space — matches an option’s value, not its label).
signal (Signal | None) – Reactive Signal two-way bound to the selected value — the option’s value, not the label shown for it. Seeding it with an option’s value selects that option and displays its text.
label (str | None) – Label displayed above the field.
message (str | None) – Hint or helper text displayed below the field.
required (bool) – If True, marks the field as required and prevents empty submission.
searchable (bool) – If True, typing in the field filters the option list. Defaults to False.
allow_custom_values (bool) – If True, users may type values not in options. Defaults to False.
group_by (str | None) – Name of an option field to cluster the popup rows under non-selectable group headers (e.g. 'category'). The field is read from each option’s flat record, so it may be any carried bag key (or 'text'/'value'). Groups appear in first-appearance order; an option missing the field renders headerless. Grouping is presentational only — value/selection are unaffected. None (default) renders a flat list.
max_visible_items (int | None) – Approximate number of option rows the popup shows before it scrolls (height is max_visible_items * row_height). Group headers and separators consume some of that budget, so the count is approximate. None (default) uses the built-in cap.
read_only (bool) – If True, the value is visible but cannot be changed — neither the dropdown arrow nor a click in the field opens the option list, and the arrow is dimmed to show it. Takes precedence over searchable and allow_custom_values while set, and restores them when cleared. Unlike disabled, the field keeps its normal appearance and stays in the tab order. Defaults to False.
disabled (bool) – If True, field is fully non-interactive and dimmed.
width (int | None) – Width in character units.
accent (AccentToken | str | None) – Accent token applied to the focus ring.
density (WidgetDensity | None) – Padding density.
localize (bool | Literal['auto'] | None) – Whether option labels (in the popup and the selected label shown in the field) are translated through the catalog — True, False, or 'auto' (translate when a translation is registered, otherwise show the literal). Defaults to the app’s localize_mode. Set False to keep proper nouns untranslated; override a single option with its localize key. When searching is enabled, search matches the displayed (translated) labels.
parent (Any) – Explicit parent widget. If omitted, the current context-stack container is used.
**kwargs (Any) – Layout placement options applied by the parent container — fill, expand, anchor, margin, row, column, sticky. See Arranging Widgets.

property addons: dict[str, Any]#: Named addon widgets inserted via insert_addon().

property disabled: bool#: Whether the field is fully non-interactive.

property error: Signal#

Reactive Signal[str] — the current validation error, '' when valid.

Bind it to surface the message anywhere, for example bs.Label(textsignal=field.error).

property group_by: str | None#

Name of the option field the popup clusters rows under, or None.

Assigning a field name groups the popup the next time it opens; assign None to render a flat list. Grouping is presentational only — it does not affect value, selection, or options.

property is_attached: bool#

Whether the widget is currently placed in its layout.

True while the widget occupies space in its parent; False after detach (or before it has ever been placed). A detached widget keeps its state and can be returned to the layout with attach.

property max_visible_items: int | None#

Approximate option-row cap before the popup scrolls, or None.

Assigning takes effect the next time the popup opens; assign None to restore the built-in cap. Height is max_visible_items * row_height, so group headers and separators make the count approximate.

property options: list[OptionDict]#

The available options as normalized {'text', 'value'} records.

Assigning a new list rebuilds the popup. Accepts the same Option forms as the constructor (strings, (text, value) tuples, or dicts).

property read_only: bool#

Whether the field is read-only — the value shows but cannot be changed.

An ordinary Select already refuses free typing, which is not the same thing. A read-only one also keeps the option list shut, from both the dropdown button and the field itself.

property schedule: Schedule#

Scheduler tied to this widget’s lifetime.

All jobs are automatically cancelled when the widget is destroyed. First access creates the Schedule instance; subsequent accesses return the same instance.

Usage:

self.schedule.delay(500, callback)
self.schedule.every(1000, tick)
job = self.schedule.idle(refresh)
job.cancel()

property selected_index: int#: Zero-based index of the selected option, or -1 if none selected.

property selection: dict | None#

The selected option as a full record dict — the data bag — or None.

{'text': ..., 'value': ..., ...any extra keys}, indexed by key like any record. None when nothing is selected or the value is a custom off-list one. Read-only.

property signal: Signal | None#: The reactive Signal bound to this field’s value, or None.

property text: str#

The label currently shown in the field — the selected option’s text.

Read-only; the complement of value (the selection’s value). Assign to value to change the selection.

property valid: Signal#

Reactive Signal[bool] — whether the field currently passes validation.

Call it to read the current state (field.valid()), subscribe to react, or bind it. Updated on every validation run — a blur, a keystroke (for key-triggered rules), or a manual validate().

property value: Any#

The currently selected value, or None if unselected.

This is the option’s value (value-space). For the displayed label, see text.

add_validation_rule(rule_type, **kwargs)#

Add a validation rule to the field.

Rules run automatically on blur or key events depending on the rule type, or manually via validate(). Multiple rules can be added; they are evaluated in order and stop at the first failure.

Rules validate the field’s typed value — a custom rule on a numeric field receives a number, on a date field a date. Text rules (stringLength, pattern, email) apply only to text fields; range applies only to numeric/date/time fields. Attaching a rule to a field whose value kind it cannot validate raises BootstackError. A Select is the exception — its value kind is whatever its options carry, so it accepts every rule type.

Parameters:

rule_type (RuleType) – The kind of validation rule to apply.
**kwargs (Any) –
Rule-specific options:
- message (all rules) — override the default error message.
- trigger (all rules) — when to run: 'always' (key and blur), 'key', 'blur', or 'manual'. Each rule type has its own sensible default (see the Validation reference).
- min, max (stringLength) — minimum/maximum character count.
- min, max (range) — lower/upper bound for the typed value (numbers, or date/time objects).
- pattern (pattern) — regex string the value must match.
- other_field (compare) — field whose value must match.
- func (custom) — callable (value) -> bool receiving the field’s typed value.

Example:

field.add_validation_rule("required")
field.add_validation_rule("stringLength", min=3, max=50)
field.add_validation_rule("email", message="Enter a valid email.")
field.add_validation_rule("custom", func=lambda v: v.isdigit())

age.add_validation_rule("range", min=18, message="Must be 18+.")

attach(**kwargs)#

Return a detached widget to its layout, optionally moving it.

With no arguments, restores the widget to exactly where detach took it from. Any layout kwargs accepted by the original placement (e.g. fill, expand, anchor, sticky, margin) override the stored options. For stacked widgets, index= sets the position among the currently attached siblings (or pass an explicit before=/after= sibling); without one, the snapshotted position is used.

Calling attach on a widget that is already attached moves it (the kwargs are re-applied). Fires on_attach.

Parameters:: **kwargs (Any) – Layout placement options to override for this placement.
Raises:: ParentResolutionError – If the widget was never placed in a layout.

capture(path, *, inset=0, settle=0.1)#

Save a picture of this widget to an image file.

Captures the area this widget occupies on screen — one widget, a whole window, or the entire application, depending on what you call it on. The file extension selects the format, so .png, .jpg, and .pdf all work.

The widget has to be visible. A capture reads pixels from the display, so the window is brought to the front first and a hidden or detached widget cannot be captured at all. Any always-on-top setting the window already had is left as it was found.

Pair it with a save dialog to let the user choose where it goes:

import bootstack as bs

def on_export():
    chosen = bs.ask_save_file(initial_file="dashboard.png")
    if chosen:
        app.capture(chosen)

Parameters:

path (str | Path) – Where to write the image. Missing parent folders are created, and the extension chooses the format.
inset (int) – Pixels to trim from every edge, zero or more. Use 2 on a whole window to drop the native border artifact.
settle (float) – Seconds to let the desktop finish repainting before the pixels are read. The default covers the common case of a dialog closing just beforehand. The interface pauses for this long, so a second click on the control that started the capture waits its turn rather than starting an overlapping one.

Returns:

The path that was written.

Raises:

BootstackError – If the widget is not visible on screen or has been scrolled out of view, if inset is negative, if no capture backend is available, or if the file cannot be written.

Return type:

Path

Added in version 0.3.0.

destroy()#

Destroy the widget and release the resources it holds.

Removes the widget from its parent, destroys its children, and cancels any pending or repeating jobs on its schedule. After this the widget must not be used again. Destroying a container destroys everything inside it.

detach()#

Remove the widget from its layout without destroying it.

The widget stops occupying space but keeps its state, children, and event bindings, ready to be returned with attach. The current position is snapshotted so a plain attach() restores it exactly — for stacked siblings this is the index among the currently attached siblings, so detaching other siblings first shifts that index.

Calling detach on a widget that is already detached, or one that was never placed in a layout, does nothing. Fires on_detach.

emit(event, *, data=None)#

Fire a named event on this widget, as if it produced the event itself.

This is how a composite widget surfaces high-level activity to its listeners, and the generic counterpart to the on_*() shorthands for firing events that have no dedicated method.

It is meant for the framework’s own events — 'change', 'select', 'input' and the rest of the data-carrying names. A handler registered through on() or an on_<event>() shorthand receives what is emitted.

Names that map onto a native event instead ('click', 'focus', 'blur', 'submit', …) are a different matter: emitting one asks the toolkit to deliver a real input event, which carries no payload and can reach handlers the widget installed for its own use. Emitting those is not a way to notify listeners, and a listener bound through on() may not see it. Drive the widget through its properties and methods instead.

Parameters:

event (str) – The event name, unprefixed — the same name you pass to on() or an on_<event>() shorthand (e.g. 'change', 'select').
data (Any) – The payload delivered to handlers. Pass the matching payload dataclass from bootstack.events — the same object an on_<event>() handler receives.

Example

from bootstack.events import ChangeEvent

field.emit("change", data=ChangeEvent(value=new_value))

insert_addon(widget, position, *, name=None, text=None, icon=None, accent=None, on_click=None, signal=None, active_when_readonly=False)#

Insert a small widget inside the field border, before or after the input.

Use this for affordances such as a clear button, a search icon, a unit suffix label, or an on/off toggle.

Parameters:

widget (Literal['button', 'label', 'toggle']) – Addon type — 'button' (clickable), 'label' (static text or icon), or 'toggle' (on/off control).
position (Literal['before', 'after']) – 'before' (left of the input) or 'after' (right).
name (str | None) – Key to retrieve the addon later via addons. Auto-generated if omitted.
text (str | None) – Text shown on the addon. Applies to any addon type.
icon (str | None) – Bootstrap Icons name shown on the addon (e.g. 'search', 'x-lg'). An icon-only addon is rendered when icon is given without text.
accent (AccentToken | str | None) – Accent token for the addon. Prefer an accent for a text-only button.
on_click (Callable[[], Any] | None) – Called with no arguments when a 'button' or 'toggle' addon is activated.
signal (Signal | None) – Reactive Signal[bool] bound to a 'toggle' addon’s on/off state.
active_when_readonly (bool) – Keep the addon interactive while the field is read-only. Off by default, so addons follow the field’s read-only state — appropriate since most act on the value (a clear button, the spin buttons). Set True only for a read-only-safe action such as a copy or reveal button; it still dims when the field is fully disabled.

Returns:

The created addon widget instance.

Return type:

Any

on(event, handler=None)#

Bind handler to event, or return a composable Stream.

With a handler — binds immediately and returns a Subscription:

sub = widget.on("change", handler)
sub.cancel()

Without a handler — returns a Stream for operator chaining. The Tk binding is created lazily when .listen() is called:

sub = widget.on("change").debounce(300).listen(handler)
sub.cancel()

Parameters:

event (str) – Event name (e.g. "change", "click").
handler (Callable[[Any], Any] | None) – Optional callback. If omitted, a Stream is returned.

Returns:

Subscription when a handler is provided; Stream otherwise.

Return type:

Stream | Subscription

on_attach(handler=None)#

Register a callback fired when the widget enters the layout.

Fires each time the widget becomes visible in its parent — on initial placement and on every attach. Pair it with on_detach to keep per-visibility resources (timers, observers) tied to the widget’s presence on screen. The handler receives a curated Event.

Parameters:: handler (Callable[[Event], Any] | None) – Called when the widget is attached. Omit to get a composable Stream.
Returns:: A cancellable Subscription when a handler is given, otherwise a Stream.
Return type:: Stream | Subscription

on_change() → Stream#

on_change(handler: Callable[[ChangeEvent], Any]) → Subscription

Register a callback fired when the selection changes.

Parameters:: handler (Callable[[ChangeEvent], Any] | None) – Called with a ChangeEvent. Omit to get a composable Stream instead.
Returns:: A cancellable Subscription when a handler is given, otherwise a Stream.
Return type:: Stream | Subscription

on_destroy(handler=None)#

Register a callback fired when the widget is destroyed.

Fires once, as the widget is torn down — the place to release resources the widget owns that aren’t cleaned up automatically (file handles, observers, external subscriptions). The handler receives a curated Event.

Parameters:: handler (Callable[[Event], Any] | None) – Called as the widget is destroyed. Omit to get a composable Stream.
Returns:: A cancellable Subscription when a handler is given, otherwise a Stream.
Return type:: Stream | Subscription

on_detach(handler=None)#

Register a callback fired when the widget leaves the layout.

Fires each time the widget stops occupying space in its parent — on detach and when an ancestor hides it. Pair it with on_attach to release per-visibility resources. The handler receives a curated Event.

Parameters:: handler (Callable[[Event], Any] | None) – Called when the widget is detached. Omit to get a composable Stream.
Returns:: A cancellable Subscription when a handler is given, otherwise a Stream.
Return type:: Stream | Subscription

on_invalid() → Stream#

on_invalid(handler: Callable[[ValidationEvent], Any]) → Subscription

Register a callback fired when validation fails.

Parameters:: handler (Callable[[ValidationEvent], Any] | None) – Called with a ValidationEvent. Omit to get a composable Stream instead.
Returns:: A cancellable Subscription when a handler is given, otherwise a Stream.
Return type:: Stream | Subscription

on_valid() → Stream#

on_valid(handler: Callable[[ValidationEvent], Any]) → Subscription

Register a callback fired when validation passes.

Parameters:: handler (Callable[[ValidationEvent], Any] | None) – Called with a ValidationEvent. Omit to get a composable Stream instead.
Returns:: A cancellable Subscription when a handler is given, otherwise a Stream.
Return type:: Stream | Subscription

on_validate() → Stream#

on_validate(handler: Callable[[ValidationEvent], Any]) → Subscription

Register a callback fired after any validation run.

Parameters:: handler (Callable[[ValidationEvent], Any] | None) – Called with a ValidationEvent. Omit to get a composable Stream instead.
Returns:: A cancellable Subscription when a handler is given, otherwise a Stream.
Return type:: Stream | Subscription

remove_addon(name)#

Remove an addon inserted with insert_addon().

Parameters:: name (str) – The addon’s name (as passed to insert_addon).
Raises:: KeyError – If no addon with that name exists.

update_addon(name, *, text=None, icon=None, accent=None, on_click=None)#

Reconfigure an existing addon in place.

Only the options you pass are changed. Use this, for example, to flip a toggle addon’s label between two units, or swap a button’s icon.

Parameters:

name (str) – The addon’s name (as passed to insert_addon).
text (str | None) – New text for the addon.
icon (str | None) – New Bootstrap Icons name for the addon.
accent (AccentToken | str | None) – New accent token for the addon.
on_click (Callable[[], Any] | None) – New click handler for a 'button' or 'toggle' addon.

Raises:

KeyError – If no addon with that name exists.

validate()#

Run validation rules against the current selection.

Rules run against the selected value, not the label shown for it, so a rule on a decoupled option list sees 'US' rather than 'United States'. A value outside the option list is displayed rather than rejected, so a custom rule is how you report one.

Returns:: True if all rules pass, False otherwise.
Return type:: bool