Read and verify exports from Python

open_export() validates canonical index.json and returns an immutable NotebookExport. Output assets remain unread until a caller decodes one output or verifies the complete export.

from marimo_export import open_export

export = open_export("dist/report")
state = export.default_state
summary = state.output("summary").json()

print(state.aliases)
print(dict(summary))

Opening and verification execute no notebook-authored browser module. Treat an HTML string or interactive module according to the consuming application's trust policy when that application later renders or mounts it.

open_export()

open_export(path: str | os.PathLike[str]) -> NotebookExport

path must be a real directory. Opening rejects a symbolic-link export root, a symbolic-link or nonregular index.json, a missing or noncanonical index, an unknown schema or codec, a declared asset larger than 64 MiB, and a declared index-plus-unique-asset closure larger than 512 MiB. Asset access and complete verification separately reject symbolic-link or nonregular asset files. Opening validates the complete declared relation without reading asset contents.

Storage that is temporarily unavailable raises ExportUnavailableError. Malformed paths, indexes, and relations raise NotebookExportError.

NotebookExport

NotebookExport is immutable. Its identity is the lowercase SHA-256 of the exact canonical index.json bytes.

Obtain a validated reader from open_export() or PreparedExport.open(). Direct NotebookExport(path, index, identity) construction accepts already parsed records and does not perform the canonical-byte, filesystem, symlink, size, or asset-closure checks owned by those opening operations. An isinstance(value, NotebookExport) check is therefore not evidence that files were opened and verified through the public reader boundary.

Properties:

export.path: Path
export.identity: str
export.spec_sha256: str
export.default_state: ExportState
export.input_names: tuple[str, ...]
export.control_bindings: Mapping[str, ControlBinding]
export.output_names: tuple[str, ...]
export.notebook: NotebookProvenance
export.producer: ProducerProvenance

default_state resolves the fingerprint selected by the authored default_state alias. control_bindings maps projection-scoped UI object IDs to root input names and typed paths.

Selection methods:

export.states() -> tuple[ExportState, ...]
export.state(alias: str) -> ExportState
export.state_by_fingerprint(fingerprint: str) -> ExportState
export.resolve(inputs: Mapping[str, JsonValue]) -> ExportState
export.verify() -> VerificationResult

state() selects an authored alias. Unknown aliases raise NotebookExportError with code state_not_found and up to 16 available aliases in details.

state_by_fingerprint() accepts a lowercase SHA-256 digest. An unknown digest raises state_not_found.

resolve() requires a complete mapping with exactly input_names. It canonicalizes the values and returns the existing state with that complete vector. Missing or extra names raise state_input_invalid. A valid vector that was not prepared raises StateUnavailableError with code state_unavailable.

ExportState

An ExportState is one exported state: a complete input vector and its named outputs in the notebook export. Several authored aliases can select the same exported state.

state.aliases: tuple[str, ...]
state.fingerprint: str
state.notebook_export: NotebookExport
state.inputs: Mapping[str, FrozenJsonValue]
state.outputs() -> tuple[ExportOutput, ...]
state.output(name: str) -> ExportOutput
state.resolve(patch: Mapping[str, JsonValue]) -> ExportState

inputs is recursively immutable. output() raises NotebookExportError with code output_not_found when name is absent.

resolve(patch) replaces the named root input values in the current complete vector, then performs exact export resolution. It does not deep-merge nested objects. An empty patch returns the same state. Unknown input names raise state_input_invalid. A resulting vector absent from the export raises StateUnavailableError.

weekly = export.default_state.resolve({"interval": "1wk"})

Resolution selects prepared data. A value outside the exported relation needs a new producer run or a Python service.

ExportOutput

An ExportOutput binds one published output name to one state and one validated descriptor.

output.name: str
output.state: ExportState
output.codec: str
output.media_type: str
output.descriptor: OutputDescriptor

output.scalar() -> None | bool | str | int | float
output.json() -> FrozenJsonValue
output.asset_bytes() -> bytes
output.blob_asset() -> BlobAsset

Choose the accessor from the descriptor codec:

Codec	Python accessor
marimo.scalar.v1	scalar()
marimo.json.v1	json()
marimo.output.v1	asset_bytes()
marimo.cell.v1	asset_bytes()
numpy.npy.v1	asset_bytes()
apache.arrow.file.v1	asset_bytes()
marimo.blob-asset.msgpack.v1	blob_asset() or asset_bytes()

Calling an accessor for another codec raises NotebookExportError with code codec_invalid.

json() returns tuples and immutable mappings. blob_asset() returns a new immutable BlobAsset with data, media_type, filename, and recursively immutable metadata.

Asset access reads one declared file, verifies its size and SHA-256, validates its native framing, and validates BlobAsset descriptor agreement where applicable. A missing or changed asset raises IntegrityError. Temporarily unavailable storage raises ExportUnavailableError.

Verify the complete asset closure

from marimo_export import verify_export

verified = verify_export("dist/report")

verify_export(path: str | os.PathLike[str]) -> VerificationResult
export.verify() -> VerificationResult

Both forms inspect the export directory, reject undeclared files under assets/, and read each unique declared asset once. VerificationResult.states counts exported states. outputs counts state-output pairs. assets counts unique asset files. bytes_verified counts those asset bytes and excludes index.json and inline values. to_dict() returns those four fields.

Verification proves consistency with index.json. It does not authenticate the person or system that produced that index. Bind provenance to a trusted index identity when producer authenticity affects the application.

Provenance records

NotebookProvenance contains:

filename: str | None
document_sha256: str

ProducerProvenance contains:

marimo: str
marimo_export: str
implementation_sha256: str

Both records are immutable and expose to_value(). Import them from marimo_export.reader when handling values returned by NotebookExport. Their defining low-level module is marimo_export.index.

Use Output representations to choose a representation for the next consumer. Use Format records and errors to inspect descriptors or implement directly against the export format.