Accessor cheat sheet

Generated from shinywidgets/_accessors.py, each renderer’s _accessor_specs (in the per-library shinywidgets/_<lib>.py modules), and the accessor methods on each render_* class in shinywidgets/_render_widget.py, on the commit documented in NOTES.md. Every accessor attaches the moment its output renders and records interactions whether or not anything has read it yet – there is no warm-up idiom and no “first read” gotcha (see “The mental model”).

Columns, straight from each AccessorSpec (not from memory):

Before any interaction: what the accessor reads before the user has ever done the thing it reports – cancels (like req(False): nothing to check, the output just doesn’t render), None, []/{}, or a real seeded value.
Across re-render: whether a re-render keeps the last interaction (the payload may then describe the previous render’s widget – see “Across re-renders”) or re-seeds from the newly rendered widget’s own current state.
Default rate: a blank means the accessor declares no policy, so the renderer’s rate_policy/rate_delay kwargs are a no-op for it (see “Rate limiting”).

Renderers with no accessors (use reactive_read() on .widget instead): render_widget, render_drawdata, render_ipysigma, render_geolibre, render_keplergl, render_ipycanvas, render_nglview, render_obsplot, render_holoviews, render_ipyfilechooser, render_pygwalker, render_vizarr, render_pyvista, render_vitessce, and render_pydeck (deprecated; pydeck >= 0.9 has no widget to read from – see render_maplibre). render_panel has one dynamic accessor, param(name) (below).

render_altair

Accessor	Returns	Before any interaction	Across re-render	Default rate
`selected(name=None)`	`IntervalSelection \\| PointSelection \\| IndexSelection`	seeded (empty selection; never `None`)	re-seeded	debounce 250ms
`selected_rows(name=None, *, df=None)`	a data frame (same type as `df`)	empty frame	derived from `selected`	debounce 250ms

render_embedding_atlas

Accessor	Returns	Before any interaction	Across re-render	Default rate
`predicate()`	`Optional[str]`	`None` (unfiltered)	re-seeded	debounce 250ms
`selected()`	native frame (pandas/polars)	all rows	derived from `predicate`	debounce 250ms

render_ipyaladin

Accessor	Returns	Before any interaction	Across re-render	Default rate
`clicked_object()`	`Optional[dict]` (`ra`, `dec`, `data`)	`None`	re-seeded	none
`selected()`	`List[astropy.Table]`	`[]`	re-seeded	none
`target()`	`SkyCoord \\| (Longitude, Latitude)`	seeded (construction-time center)	re-seeded	none
`fov()`	`astropy.Angle`	seeded (construction-time fov)	re-seeded	none

render_ipyleaflet / render_leafmap

Both share _IpyleafletAccessors; on render_leafmap, calling any of these on a non-ipyleaflet backend (maplibre, plotly, …) raises TypeError pointing at reactive_read().

Accessor	Returns	Before any interaction	Across re-render	Default rate
`bounds()`	`((south, west), (north, east))`	cancels until the browser’s first report	re-seeded	none
`zoom()`	`float`	seeded (construction-time zoom)	re-seeded	none
`center()`	`[lat, lng]`	seeded (construction-time center)	re-seeded	none
`clicked()`	`Optional[dict]` (`coordinates: [lat, lng]`)	`None`	kept	none
`drawn_features()`	`List[GeoJSON Feature dict]`	`[]`, or raises `TypeError` if the map has no `DrawControl`	re-seeded	none

render_itables

Accessor	Returns	Before any interaction	Across re-render	Default rate
`selected_rows()`	`List[int]`	`[]`. Requires `select=True`	re-seeded	none

render_jscatter

Accessor	Returns	Before any interaction	Across re-render	Default rate
`selected()`	`numpy.ndarray[uint32]`	cancels until the browser’s first report	re-seeded	none
`selected_rows(df=None)`	the selected rows of `df` (default: the `Scatter`’s data frame), same type as `df`	empty frame (cancels when `selected()` does)	derived from `selected`	none

render_k3d

Accessor	Returns	Before any interaction	Across re-render	Default rate
`camera()`	`List[float]` (9 floats: position, target, up)	cancels until the browser auto-fits (forever with `camera_auto_fit=False` and no explicit camera)	re-seeded	none (k3d itself throttles to ~1/200ms)

render_ipycytoscape

Accessor	Returns	Before any interaction	Across re-render	Default rate
`clicked_node()`	`Optional[dict]` (`ele.json()`)	`None`	kept	none
`clicked_edge()`	`Optional[dict]` (`ele.json()`)	`None`	kept	none
`selected_nodes()`	`List[dict]` (node data)	`[]`	re-seeded	debounce 250ms
`selected_edges()`	`List[dict]` (edge data)	`[]`	re-seeded	debounce 250ms

Renamed from node_clicked()/edge_clicked() (#441, naming convention: interaction first).

render_bqplot

Accessor	Returns	Before any interaction	Across re-render	Default rate
`selected()`	`List[Optional[np.ndarray]]`, aligned with `fig.marks`	seeded (`None` per mark)	re-seeded	debounce 250ms
`selected_rows(df, *, mark=None)`	the rows of `df` (required; same type as `df`) at one mark’s selected positions	empty frame (cancels when `selected()` does)	derived from `selected`	debounce 250ms
`brush()`	`Optional[np.ndarray \\| dict]`	`None`	re-seeded	debounce 250ms

No clicked(): element_click messages never reach marks while the figure has an interaction (its overlay intercepts clicks) – deliberately omitted rather than ship an accessor that’s silently dead in the common case.

render_ipyvolume

Accessor	Returns	Before any interaction	Across re-render	Default rate
`camera()`	live `pythreejs.Camera`	cancels while the figure has no camera	re-seeded	none

render_lonboard

Accessor	Returns	Before any interaction	Across re-render	Default rate
`view_state()`	`MapViewState \\| GlobeViewState`	seeded (computed from the layers at construction)	re-seeded	debounce 250ms (#400)
`selected()`	`Optional[int]`	`None`	re-seeded (seeded from whichever layer retains a pick on its own `selected_index` trait – `None` again for freshly built layers)	none
`selected_rows(df=None)`	the picked row of `df` (default: rebuilt from the single pickable layer’s own data; raises with several), in `df`’s own type	empty frame	derived from `selected()`	none
`selected_bounds()`	`Optional[(minx, miny, maxx, maxy)]`	`None`	re-seeded	none
`clicked()`	`Optional[(lng, lat)]`	`None`. Reading it is what turns on click reporting in the browser	kept	none

[up] GlobeView permanently breaks view_state() (and reactive_read() on the trait): the browser sends pitch/bearing, which GlobeViewState has no fields for, so the first sync throws (swallowed) and it never updates.

render_maplibre

Accessor	Returns	Before any interaction	Across re-render	Default rate
`view_state()`	`{center, zoom, bounds, bearing, pitch}`	cancels (`req(False)`) until the browser’s first report (the map’s `load` event)	kept until the new map reports, then re-seeded	none (the browser reports once per completed gesture, not per frame)
`clicked()`	`Optional[{lng, lat}]`	`None`	kept	none
`drawn_features()`	list of drawn GeoJSON features	`[]`	re-seeded (the new map’s empty set)	none

render_matplotlib / render_plotnine

Accessor	Returns	Before any interaction	Across re-render	Default rate
`clicked()`	`Optional[matplotlib.backend_bases.MouseEvent]`	`None`	kept	none
`picked()`	`Optional[matplotlib.backend_bases.PickEvent]`	`None`. (`render_matplotlib` only.)	kept	none
`limits(ax=0)`	`((x0, x1), (y0, y1))`	seeded (current view limits)	re-seeded	debounce 250ms

Every press fires clicked() (no dedup – MouseEvent has no equality); a double-click is 3 presses, not 2. render_plotnine has only clicked().

render_bokeh

Accessor	Returns	Before any interaction	Across re-render	Default rate
`selected()`	`List[int]`	`[]` (never `None` – #437)	re-seeded	debounce 250ms
`selected_rows()`	`pd.DataFrame`	empty frame	derived from `selected` + `source_data` trigger	debounce 250ms
`tapped()`	`Optional[bokeh.events.Tap]`	`None`	kept	none
`zoomed()`	`Optional[bokeh.events.RangesUpdate]`	`None` until the first gesture (an auto-fitting or categorical range has nothing to seed)	re-seeded	none

[up] jupyter_bokeh fires the underlying on_change/on_event callback twice per browser change; the accessors’ input-priority dedup absorbs this (counted once), but a raw source.selected.on_change(...) callback you register yourself will see two calls.

render_mosaic_widget

Accessor	Returns	Before any interaction	Across re-render	Default rate
`params()`	`Dict[str, {"value", "predicate"}]`	`{}`	re-seeded	debounce 250ms
`data(table=None)`	lazy `duckdb.DuckDBPyRelation`	rows unfiltered	derived from `params` (reads the live trait, not the debounced value)	debounce 250ms (inherited)

render_perspective

Accessor	Returns	Before any interaction	Across re-render	Default rate
`filter()`	`List[[col, op, value]]`	`[]`	re-seeded	none
`view_config()`	`Dict` (`plugin`, `columns`, `group_by`, `split_by`, `aggregates`, `sort`, `filter`, `expressions`)	seeded (construction-time config)	re-seeded	none

Row clicks/selections never reach Python.

render_ipydatagrid

Accessor	Returns	Before any interaction	Across re-render	Default rate
`selected()`	`List[{"r1","r2","c1","c2"}]`	`[]`	re-seeded	debounce 250ms (#400)
`clicked_cell()`	`Optional[dict]`	`None`	kept	none
`edited_cell()`	`Optional[dict]`	`None`	kept	none
`visible_data()`	`pd.DataFrame`	the whole frame	re-seeded (derived trigger)	none

Renamed from cell_clicked() (#441). selected() now debounces by default (#400) – it used to be the canonical “no policy” example in this article; see “Rate limiting” for the current one.

render_plotly

Accessor	Returns	Before any interaction	Across re-render	Default rate
`clicked()`	`Optional[pd.DataFrame]`	`None`	kept	none
`selected()`	`Optional[pd.DataFrame]`	`None`	kept (the new plot’s own empty selection replaces it once it reports – see note)	none
`selecting()`	`Optional[pd.DataFrame]`	`None`	kept	debounce 250ms
`brushed()`	`Optional[dict]` (`range` or `lassoPoints`)	`None`	kept (same note as `selected()`)	none
`brushing()`	`Optional[dict]`	`None`	kept	debounce 250ms
`relayout()`	`Optional[dict]`	`None`	kept (a delta payload; refers to the previous render’s plot)	none
`hover()`	`Optional[pd.DataFrame]`	`None`	kept	debounce 250ms
`double_clicked()`	`Optional[bool]`	`None`	kept (pulse: re-fires readers on every subsequent double-click even though the value stays `True`)	none
`legend_clicked()`	`Optional[pd.DataFrame]`	`None`	kept (pulse: re-fires on every click, even of the same item)	none
`visible_traces()`	`Optional[pd.DataFrame]`	seeded (the figure’s initial trace visibility)	re-seeded	none
`selected_rows(df, *, key=None)`	same frame type as `df`	empty frame	derived from `selected`	none

selected()/brushed() attach at render like every other accessor (#419): a box or lasso selection made before the first read is reported, not lost. They don’t reset to None on their own re-render the instant it happens – plotly.js’s bridge also rebuilds and re-sends the new graph div’s own (initially empty) selection shortly after mount, which is what actually clears them; until that arrives, the old value is still what reads back. double_clicked()/legend_clicked() are pulses (priority="event"): identical values still re-fire readers, unlike every other accessor here, which dedupes. [docs]: a plain click also resets selected()/brushed() when dragmode="select"/"lasso" (a zero-area selection) – affects apps combining click-detail with lasso on one figure.

render_pythreejs

Accessor	Returns	Before any interaction	Across re-render	Default rate
`camera()`	live `pythreejs.Camera`	seeded (the Python-constructed camera; pythreejs doesn’t sync at mount)	re-seeded	none

Same shape as render_ipyvolume’s camera().

render_quak

Accessor	Returns	Before any interaction	Across re-render	Default rate
`sql()`	`str`	cancels while the frontend is still initializing (empty string)	re-seeded	debounce 250ms
`data()`	lazy `duckdb.DuckDBPyRelation`	the construction query’s rows	derived from `sql` (reads the published, not live, query)	debounce 250ms (inherited)

render_rerun

Accessor	Returns	Before any interaction	Across re-render	Default rate
`selected()`	`Optional[rerun.notebook.SelectionChangeEvent]`	`None` until the user first selects something	kept (the new viewer’s load-time empty report is ignored)	none

render_mols2grid

Accessor	Returns	Before any interaction	Across re-render	Default rate
`selected()`	`Optional[Dict[int, str]]` (`{row_index: SMILES}`)	`{}`	re-seeded	none
`clicked()`	`Optional[dict]`	`None`. Only exists with `clicks=True` or a Python `callback`	kept	none

Clicking the same molecule twice doesn’t re-fire clicked() (a mols2grid limitation: the trait only changes when the payload does – unlike plotly’s clicked(), there’s no underlying event stream to re-publish from).

render_niivue

Accessor	Returns	Before any interaction	Across re-render	Default rate
`location()`	`Optional[dict]` (`ax_cor_sag`, `frac`, `mm`, `vox`, `values`, `string`, `xy`)	`None` (not sent on load)	re-seeded	debounce 250ms

render_reactable

All five attach at render and seed from the browser’s own getState() response (so a sort or selection made before the first read is reflected), confirmed working on current main – the _accessor_specs typo that broke every one of these (missing leading underscore, shinywidgets/_render_widget.py) is fixed.

Accessor	Returns	Before any interaction	Across re-render	Default rate
`selected_rows()`	`List[int]`	cancels until the browser first reports	re-seeded	none
`page()`	`int`	cancels until the browser first reports	re-seeded	none
`sorted()`	`List[{"id","desc"}]`	cancels until the browser first reports	re-seeded	none
`filtered()`	`List[{"id","value"}]`	cancels until the browser first reports	re-seeded	debounce 250ms
`search()`	`str`	cancels until the browser first reports	re-seeded	debounce 250ms

All five share “0-based, data-ordered positions survive sort/filter/paging” for selected_rows() and page()/sorted()/filtered()’s own semantics. [docs]: the class docstring says in-place props["data"] updates have no effect; verified they work and preserve sort/filter/page/selection (reactable-py’s mounted component doesn’t memoize data).

render_panel

Accessor	Returns	Before any interaction	Across re-render	Default rate
`param(name)`	the parameter’s type	seeded (the parameter’s current value)	re-seeded, and re-fires even on an unchanged value (`priority="event"`, so following a re-rendered object’s identity doesn’t get swallowed as a dedup)	none

param(name) is a dynamic accessor (the name isn’t known ahead of time): the rendered object must be a param.Parameterized (a panel widget, pane, or Viewer), or it raises TypeError; an unknown parameter name raises ValueError listing the object’s actual parameters.