Read results

NotebookView.state reports browser work as one consistent, read-only snapshot.

import marimo as mo
import observablejs as obs

notebook = obs.Notebook(
    obs.ojs(
        'viewof gain = Inputs.range([0, 12], {value: 5, step: 1, label: "Gain"})',
        key="gain_control",
    ),
    obs.js("const doubled = gain * 2;", key="doubled", display=False),
    obs.js(
        'html`<p>Gain is <strong>${gain}</strong>. Doubled is <strong>${doubled}</strong>.</p>`',
        key="readout",
    ),
)

view = notebook.view()
widget = mo.ui.anywidget(view)
widget

Read a result after the latest input revision settles:

widget.value  # rerun this cell when synchronized widget state changes
state = view.state

if (
    not state.pending
    and state.input_revision is not None
    and state.settled_revision == state.input_revision
):
    doubled = state.result("doubled")
    if doubled.status == "success":
        print(doubled.values["doubled"])
    else:
        print(doubled.errors)

Each CellResult has a status, revision, read-only values, and structured errors. A failed output reports its error phase and optional variable name. A multi-output cell may contain successful values beside errors.

React to state changes

Traitlets-aware environments can observe the public state trait:

def on_state(change):
    state = change["new"]
    if not state.pending:
        print(state.results)

view.observe(on_state, names="state")

In marimo, reference the wrapped widget in the reading cell so that the cell reruns when synchronized widget state changes, then read view.state from the underlying view.

State belongs to the view whose runtime produced it. A focused view reports its selected result while hidden dependencies still evaluate:

gain_view = notebook.view("gain_control")

See View state and graph for revision, status, error, and value conversion contracts.