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API reference

Top-level functions

zarr.open

node = zarr.open(store)
node = zarr.open(store, Path="group/array")

Open an existing array or group; returns zarr.Array or zarr.Group. store is a directory path or a store object. Errors with zarr:NodeNotFound if no zarr.json exists at the path.

zarr.create

z = zarr.create(store, shape, dtype, Name=Value...)

Create an array (see Arrays for the full option table). shape is the Zarr shape: [m n ...], a scalar n (rank-1), or [] (rank-0). dtype accepts MATLAB class names, Zarr names, "string", "bytes", or "datetime64[<unit>]" / "timedelta64[<unit>]".

Options: Path, ChunkShape, ShardShape, IndexLocation, Codecs, FillValue, Attributes, DimensionNames, Order, ChunkKeyEncoding, WriteEmptyChunks, Overwrite.

zarr.create_group

g = zarr.create_group(store, Path="a/b", Attributes=struct(...))

Create a group (and any missing parents). Idempotent for existing groups.

zarr.consolidate_metadata

zarr.consolidate_metadata(store)

Inline all node metadata into the root group's zarr.json (zarr-python-compatible). Re-run after changing the hierarchy.

zarr.delete_node

zarr.delete_node(store, path)

Recursively remove an array or group and all data beneath it.

zarr.Array

Handle class returned by zarr.open/zarr.create.

Properties (read-only): store, path, meta, shape (Zarr shape), dtype (Zarr name), chunkShape, attrs (struct), dimensionNames. Settable: writeEmptyChunks (default false).

Indexing: full MATLAB paren indexing — slices, end, :, numeric and logical fancy indexing, scalar expansion on assignment. z(:) reads the whole array as a column.

Methods:

Method Description
read(start, count) region read, 1-based; count may contain Inf; both optional
write(data, start) region write; start optional (defaults to origin)
resize(newShape) change shape; shrinking deletes out-of-bounds chunks
append(data, dim) grow along dim and write data at the end
setAttr(name, value) / setAttrs(s) update / replace attributes
size / ndims / numel / disp standard MATLAB semantics

zarr.Group

Properties: store, path, meta, attrs.

Method Description
item(name) open a child (accepts nested paths, e.g. "a/b")
isKey(name) does a child node exist
children() [arrayNames, groupNames], both string columns
createArray(name, shape, dtype, ...) like zarr.create under this group
createGroup(name, ...) create a child group
setAttr / setAttrs attribute updates
tree(maxDepth) print the hierarchy

Both item and children are served from consolidated metadata when present (no store reads).

Stores (zarr.stores.*)

Class Constructor Notes
LocalStore LocalStore(root) directory; atomic writes, ranged reads
MemoryStore MemoryStore() in-memory
ZipStore ZipStore(path, Mode="r"/"w") one-file store; "w" finalizes on close()
HttpStore HttpStore(baseUrl) read-only; Range requests for partial reads

Custom backends subclass zarr.stores.Store: implement get, set, erase, exists, list, listDir; optionally override getPartial(key, offset, len) and getSuffix(key, len) for ranged reads.

Codecs (zarr.codecs.*)

Class Constructor
ZstdCodec ZstdCodec(level, checksum) — level −131072…22 (default 0), checksum logical
BloscCodec BloscCodec(cname="zstd", clevel=5, shuffle="shuffle", typesize=0, blocksize=0)
GzipCodec GzipCodec(level) — 0…9, default 5
Crc32cCodec Crc32cCodec()
TransposeCodec TransposeCodec(order) — 0-based permutation
BytesCodec BytesCodec(endian) — "little" (default) / "big"
ShardingCodec ShardingCodec(innerChunkShape, Codecs={...}, IndexCodecs={...}, IndexLocation="end")
VlenUtf8Codec / VlenBytesCodec VlenUtf8Codec() / VlenBytesCodec() — inserted automatically for string/bytes dtypes

Error identifiers

All errors use the zarr: prefix; the ones worth catching:

zarr:NodeNotFound, zarr:NodeExists, zarr:Indexing, zarr:ShapeMismatch, zarr:UnsupportedCodec, zarr:MissingMex, zarr:ChecksumError, zarr:CodecError, zarr:InvalidMetadata, zarr:StoreError.