.. only:: doctest

   >>> import shutil
   >>> shutil.rmtree('data', ignore_errors=True)

.. _user-guide-arrays:

Working with arrays
===================

Creating an array
-----------------

Zarr has several functions for creating arrays. For example::

   >>> import zarr
   >>> store = zarr.storage.MemoryStore()
   >>> z = zarr.create_array(store=store, shape=(10000, 10000), chunks=(1000, 1000), dtype='int32')
   >>> z
   <Array memory://... shape=(10000, 10000) dtype=int32>

The code above creates a 2-dimensional array of 32-bit integers with 10000 rows
and 10000 columns, divided into chunks where each chunk has 1000 rows and 1000
columns (and so there will be 100 chunks in total). The data is written to a
:class:`zarr.storage.MemoryStore` (e.g. an in-memory dict). See
:ref:`user-guide-persist` for details on storing arrays in other stores.

For a complete list of array creation routines see the :mod:`zarr`
module documentation.

.. _user-guide-array:

Reading and writing data
------------------------

Zarr arrays support a similar interface to `NumPy <https://numpy.org/doc/stable/>`_
arrays for reading and writing data. For example, the entire array can be filled
with a scalar value::

   >>> z[:] = 42

Regions of the array can also be written to, e.g.::

   >>> import numpy as np
   >>>
   >>> z[0, :] = np.arange(10000)
   >>> z[:, 0] = np.arange(10000)

The contents of the array can be retrieved by slicing, which will load the
requested region into memory as a NumPy array, e.g.::

   >>> z[0, 0]
   array(0, dtype=int32)
   >>> z[-1, -1]
   array(42, dtype=int32)
   >>> z[0, :]
   array([   0,    1,    2, ..., 9997, 9998, 9999],
         shape=(10000,), dtype=int32)
   >>> z[:, 0]
   array([   0,    1,    2, ..., 9997, 9998, 9999],
         shape=(10000,), dtype=int32)
   >>> z[:]
   array([[   0,    1,    2, ..., 9997, 9998, 9999],
          [   1,   42,   42, ...,   42,   42,   42],
          [   2,   42,   42, ...,   42,   42,   42],
          ...,
          [9997,   42,   42, ...,   42,   42,   42],
          [9998,   42,   42, ...,   42,   42,   42],
          [9999,   42,   42, ...,   42,   42,   42]],
         shape=(10000, 10000), dtype=int32)

Read more about NumPy-style indexing can be found in the
`NumPy documentation <https://numpy.org/doc/stable/user/basics.indexing.html>`_.

.. _user-guide-persist:

Persistent arrays
-----------------

In the examples above, compressed data for each chunk of the array was stored in
main memory. Zarr arrays can also be stored on a file system, enabling
persistence of data between sessions. To do this, we can change the store
argument to point to a filesystem path::

   >>> z1 = zarr.create_array(store='data/example-1.zarr', shape=(10000, 10000), chunks=(1000, 1000), dtype='int32')

The array above will store its configuration metadata and all compressed chunk
data in a directory called ``'data/example-1.zarr'`` relative to the current working
directory. The :func:`zarr.create_array` function provides a convenient way
to create a new persistent array or continue working with an existing
array. Note, there is no need to close an array: data are automatically
flushed to disk, and files are automatically closed whenever an array is modified.

Persistent arrays support the same interface for reading and writing data,
e.g.::

   >>> z1[:] = 42
   >>> z1[0, :] = np.arange(10000)
   >>> z1[:, 0] = np.arange(10000)

Check that the data have been written and can be read again::

   >>> z2 = zarr.open_array('data/example-1.zarr', mode='r')
   >>> np.all(z1[:] == z2[:])
   np.True_

If you are just looking for a fast and convenient way to save NumPy arrays to
disk then load back into memory later, the functions
:func:`zarr.save` and :func:`zarr.load` may be
useful. E.g.::

   >>> a = np.arange(10)
   >>> zarr.save('data/example-2.zarr', a)
   >>> zarr.load('data/example-2.zarr')
   array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

Please note that there are a number of other options for persistent array
storage, see the :ref:`Storage Guide <user-guide-storage>` guide for more details.

.. _user-guide-resize:

Resizing and appending
----------------------

A Zarr array can be resized, which means that any of its dimensions can be
increased or decreased in length. For example::

   >>> z = zarr.create_array(store='data/example-3.zarr', shape=(10000, 10000), dtype='int32',chunks=(1000, 1000))
   >>> z[:] = 42
   >>> z.shape
   (10000, 10000)
   >>> z.resize((20000, 10000))
   >>> z.shape
   (20000, 10000)

Note that when an array is resized, the underlying data are not rearranged in
any way. If one or more dimensions are shrunk, any chunks falling outside the
new array shape will be deleted from the underlying store.

:func:`zarr.Array.append` is provided as a convenience function, which can be
used to append data to any axis. E.g.::

   >>> a = np.arange(10000000, dtype='int32').reshape(10000, 1000)
   >>> z = zarr.create_array(store='data/example-4.zarr', shape=a.shape, dtype=a.dtype, chunks=(1000, 100))
   >>> z[:] = a
   >>> z.shape
   (10000, 1000)
   >>> z.append(a)
   (20000, 1000)
   >>> z.append(np.vstack([a, a]), axis=1)
   (20000, 2000)
   >>> z.shape
   (20000, 2000)

.. _user-guide-compress:

Compressors
-----------

A number of different compressors can be used with Zarr. Zarr includes Blosc,
Zstandard and Gzip compressors. Additional compressors are available through
a separate package called NumCodecs_ which provides various
compressor libraries including LZ4, Zlib, BZ2 and LZMA.
Different compressors can be provided via the ``compressors`` keyword
argument accepted by all array creation functions. For example::

   >>> compressors = zarr.codecs.BloscCodec(cname='zstd', clevel=3, shuffle=zarr.codecs.BloscShuffle.bitshuffle)
   >>> data = np.arange(100000000, dtype='int32').reshape(10000, 10000)
   >>> z = zarr.create_array(store='data/example-5.zarr', shape=data.shape, dtype=data.dtype, chunks=(1000, 1000), compressors=compressors)
   >>> z[:] = data
   >>> z.compressors
   (BloscCodec(typesize=4, cname=<BloscCname.zstd: 'zstd'>, clevel=3, shuffle=<BloscShuffle.bitshuffle: 'bitshuffle'>, blocksize=0),)

This array above will use Blosc as the primary compressor, using the Zstandard
algorithm (compression level 3) internally within Blosc, and with the
bit-shuffle filter applied.

When using a compressor, it can be useful to get some diagnostics on the
compression ratio. Zarr arrays provide the :attr:`zarr.Array.info` property
which can be used to print useful diagnostics, e.g.::

   >>> z.info
   Type               : Array
   Zarr format        : 3
   Data type          : DataType.int32
   Shape              : (10000, 10000)
   Chunk shape        : (1000, 1000)
   Order              : C
   Read-only          : False
   Store type         : LocalStore
   Filters            : ()
   Serializer         : BytesCodec(endian=<Endian.little: 'little'>)
   Compressors        : (BloscCodec(typesize=4, cname=<BloscCname.zstd: 'zstd'>, clevel=3, shuffle=<BloscShuffle.bitshuffle: 'bitshuffle'>, blocksize=0),)
   No. bytes          : 400000000 (381.5M)

The :func:`zarr.Array.info_complete` method inspects the underlying store and
prints additional diagnostics, e.g.::

   >>> z.info_complete()
   Type               : Array
   Zarr format        : 3
   Data type          : DataType.int32
   Shape              : (10000, 10000)
   Chunk shape        : (1000, 1000)
   Order              : C
   Read-only          : False
   Store type         : LocalStore
   Filters            : ()
   Serializer         : BytesCodec(endian=<Endian.little: 'little'>)
   Compressors        : (BloscCodec(typesize=4, cname=<BloscCname.zstd: 'zstd'>, clevel=3, shuffle=<BloscShuffle.bitshuffle: 'bitshuffle'>, blocksize=0),)
   No. bytes          : 400000000 (381.5M)
   No. bytes stored   : 9696520
   Storage ratio      : 41.3
   Chunks Initialized : 100

.. note::
   :func:`zarr.Array.info_complete` will inspect the underlying store and may
   be slow for large arrays. Use :attr:`zarr.Array.info` if detailed storage
   statistics are not needed.

If you don't specify a compressor, by default Zarr uses the Zstandard
compressor.

In addition to Blosc and Zstandard, other compression libraries can also be used. For example,
here is an array using Gzip compression, level 1::

   >>> data = np.arange(100000000, dtype='int32').reshape(10000, 10000)
   >>> z = zarr.create_array(store='data/example-6.zarr', shape=data.shape, dtype=data.dtype, chunks=(1000, 1000), compressors=zarr.codecs.GzipCodec(level=1))
   >>> z[:] = data
   >>> z.compressors
   (GzipCodec(level=1),)

Here is an example using LZMA from NumCodecs_ with a custom filter pipeline including LZMA's
built-in delta filter::

   >>> import lzma
   >>> from numcodecs.zarr3 import LZMA
   >>>
   >>> lzma_filters = [dict(id=lzma.FILTER_DELTA, dist=4), dict(id=lzma.FILTER_LZMA2, preset=1)]
   >>> compressors = LZMA(filters=lzma_filters)
   >>> data = np.arange(100000000, dtype='int32').reshape(10000, 10000)
   >>> z = zarr.create_array(store='data/example-7.zarr', shape=data.shape, dtype=data.dtype, chunks=(1000, 1000), compressors=compressors)
   >>> z.compressors
   (LZMA(codec_name='numcodecs.lzma', codec_config={'filters': [{'id': 3, 'dist': 4}, {'id': 33, 'preset': 1}]}),)

The default compressor can be changed by setting the value of the using Zarr's
:ref:`user-guide-config`, e.g.::

   >>> with zarr.config.set({'array.v2_default_compressor.numeric': {'id': 'blosc'}}):
   ...     z = zarr.create_array(store={}, shape=(100000000,), chunks=(1000000,), dtype='int32', zarr_format=2)
   >>> z.filters
   ()
   >>> z.compressors
   (Blosc(cname='lz4', clevel=5, shuffle=SHUFFLE, blocksize=0),)

To disable compression, set ``compressors=None`` when creating an array, e.g.::

   >>> z = zarr.create_array(store='data/example-8.zarr', shape=(100000000,), chunks=(1000000,), dtype='int32', compressors=None)
   >>> z.compressors
   ()

.. _user-guide-filters:

Filters
-------

In some cases, compression can be improved by transforming the data in some
way. For example, if nearby values tend to be correlated, then shuffling the
bytes within each numerical value or storing the difference between adjacent
values may increase compression ratio. Some compressors provide built-in filters
that apply transformations to the data prior to compression. For example, the
Blosc compressor has built-in implementations of byte- and bit-shuffle filters,
and the LZMA compressor has a built-in implementation of a delta
filter. However, to provide additional flexibility for implementing and using
filters in combination with different compressors, Zarr also provides a
mechanism for configuring filters outside of the primary compressor.

Here is an example using a delta filter with the Blosc compressor::

   >>> from numcodecs.zarr3 import Delta
   >>>
   >>> filters = [Delta(dtype='int32')]
   >>> compressors = zarr.codecs.BloscCodec(cname='zstd', clevel=1, shuffle=zarr.codecs.BloscShuffle.shuffle)
   >>> data = np.arange(100000000, dtype='int32').reshape(10000, 10000)
   >>> z = zarr.create_array(store='data/example-9.zarr', shape=data.shape, dtype=data.dtype, chunks=(1000, 1000), filters=filters, compressors=compressors)
   >>> z.info
   Type               : Array
   Zarr format        : 3
   Data type          : DataType.int32
   Shape              : (10000, 10000)
   Chunk shape        : (1000, 1000)
   Order              : C
   Read-only          : False
   Store type         : LocalStore
   Filters            : (Delta(codec_name='numcodecs.delta', codec_config={'dtype': 'int32'}),)
   Serializer         : BytesCodec(endian=<Endian.little: 'little'>)
   Compressors        : (BloscCodec(typesize=4, cname=<BloscCname.zstd: 'zstd'>, clevel=1, shuffle=<BloscShuffle.shuffle: 'shuffle'>, blocksize=0),)
   No. bytes          : 400000000 (381.5M)

For more information about available filter codecs, see the `Numcodecs
<https://numcodecs.readthedocs.io/>`_ documentation.

.. _user-guide-indexing:

Advanced indexing
-----------------

Zarr arrays support several methods for advanced or "fancy"
indexing, which enable a subset of data items to be extracted or updated in an
array without loading the entire array into memory.

Note that although this functionality is similar to some of the advanced
indexing capabilities available on NumPy arrays and on h5py datasets, **the Zarr
API for advanced indexing is different from both NumPy and h5py**, so please
read this section carefully.  For a complete description of the indexing API,
see the documentation for the :class:`zarr.Array` class.

Indexing with coordinate arrays
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Items from a Zarr array can be extracted by providing an integer array of
coordinates. E.g.::

   >>> data = np.arange(10) ** 2
   >>> z = zarr.create_array(store='data/example-10.zarr', shape=data.shape, dtype=data.dtype)
   >>> z[:] = data
   >>> z[:]
   array([ 0,  1,  4,  9, 16, 25, 36, 49, 64, 81])
   >>> z.get_coordinate_selection([2, 5])
   array([ 4, 25])

Coordinate arrays can also be used to update data, e.g.::

   >>> z.set_coordinate_selection([2, 5], [-1, -2])
   >>> z[:]
   array([ 0,  1, -1,  9, 16, -2, 36, 49, 64, 81])

For multidimensional arrays, coordinates must be provided for each dimension,
e.g.::

   >>> data = np.arange(15).reshape(3, 5)
   >>> z = zarr.create_array(store='data/example-11.zarr', shape=data.shape, dtype=data.dtype)
   >>> z[:] = data
   >>> z[:]
   array([[ 0,  1,  2,  3,  4],
          [ 5,  6,  7,  8,  9],
          [10, 11, 12, 13, 14]])
   >>> z.get_coordinate_selection(([0, 2], [1, 3]))
   array([ 1, 13])
   >>> z.set_coordinate_selection(([0, 2], [1, 3]), [-1, -2])
   >>> z[:]
   array([[ 0, -1,  2,  3,  4],
          [ 5,  6,  7,  8,  9],
          [10, 11, 12, -2, 14]])

For convenience, coordinate indexing is also available via the ``vindex``
property, as well as the square bracket operator, e.g.::

   >>> z.vindex[[0, 2], [1, 3]]
   array([-1, -2])
   >>> z.vindex[[0, 2], [1, 3]] = [-3, -4]
   >>> z[:]
   array([[ 0, -3,  2,  3,  4],
          [ 5,  6,  7,  8,  9],
          [10, 11, 12, -4, 14]])
   >>> z[[0, 2], [1, 3]]
   array([-3, -4])

When the indexing arrays have different shapes, they are broadcast together.
That is, the following two calls are equivalent::

   >>> z[1, [1, 3]]
   array([6, 8])
   >>> z[[1, 1], [1, 3]]
   array([6, 8])

Indexing with a mask array
~~~~~~~~~~~~~~~~~~~~~~~~~~

Items can also be extracted by providing a Boolean mask. E.g.::

   >>> data = np.arange(10) ** 2
   >>> z = zarr.create_array(store='data/example-12.zarr', shape=data.shape, dtype=data.dtype)
   >>> z[:] = data
   >>> z[:]
   array([ 0,  1,  4,  9, 16, 25, 36, 49, 64, 81])
   >>> sel = np.zeros_like(z, dtype=bool)
   >>> sel[2] = True
   >>> sel[5] = True
   >>> z.get_mask_selection(sel)
   array([ 4, 25])
   >>> z.set_mask_selection(sel, [-1, -2])
   >>> z[:]
   array([ 0,  1, -1,  9, 16, -2, 36, 49, 64, 81])

Here's a multidimensional example::

   >>> data = np.arange(15).reshape(3, 5)
   >>> z = zarr.create_array(store='data/example-13.zarr', shape=data.shape, dtype=data.dtype)
   >>> z[:] = data
   >>> z[:]
   array([[ 0,  1,  2,  3,  4],
          [ 5,  6,  7,  8,  9],
          [10, 11, 12, 13, 14]])
   >>> sel = np.zeros_like(z, dtype=bool)
   >>> sel[0, 1] = True
   >>> sel[2, 3] = True
   >>> z.get_mask_selection(sel)
   array([ 1, 13])
   >>> z.set_mask_selection(sel, [-1, -2])
   >>> z[:]
   array([[ 0, -1,  2,  3,  4],
          [ 5,  6,  7,  8,  9],
          [10, 11, 12, -2, 14]])

For convenience, mask indexing is also available via the ``vindex`` property,
e.g.::

   >>> z.vindex[sel]
   array([-1, -2])
   >>> z.vindex[sel] = [-3, -4]
   >>> z[:]
   array([[ 0, -3,  2,  3,  4],
          [ 5,  6,  7,  8,  9],
          [10, 11, 12, -4, 14]])

Mask indexing is conceptually the same as coordinate indexing, and is
implemented internally via the same machinery. Both styles of indexing allow
selecting arbitrary items from an array, also known as point selection.

Orthogonal indexing
~~~~~~~~~~~~~~~~~~~

Zarr arrays also support methods for orthogonal indexing, which allows
selections to be made along each dimension of an array independently. For
example, this allows selecting a subset of rows and/or columns from a
2-dimensional array. E.g.::

   >>> data = np.arange(15).reshape(3, 5)
   >>> z = zarr.create_array(store='data/example-14.zarr', shape=data.shape, dtype=data.dtype)
   >>> z[:] = data
   >>> z[:]
   array([[ 0,  1,  2,  3,  4],
          [ 5,  6,  7,  8,  9],
          [10, 11, 12, 13, 14]])
   >>> z.get_orthogonal_selection(([0, 2], slice(None)))  # select first and third rows
   array([[ 0,  1,  2,  3,  4],
          [10, 11, 12, 13, 14]])
   >>> z.get_orthogonal_selection((slice(None), [1, 3]))  # select second and fourth columns
   array([[ 1,  3],
          [ 6,  8],
          [11, 13]])
   >>> z.get_orthogonal_selection(([0, 2], [1, 3]))  # select rows [0, 2] and columns [1, 4]
   array([[ 1,  3],
          [11, 13]])

Data can also be modified, e.g.::

   >>> z.set_orthogonal_selection(([0, 2], [1, 3]), [[-1, -2], [-3, -4]])

For convenience, the orthogonal indexing functionality is also available via the
``oindex`` property, e.g.::

   >>> data = np.arange(15).reshape(3, 5)
   >>> z = zarr.create_array(store='data/example-15.zarr', shape=data.shape, dtype=data.dtype)
   >>> z[:] = data
   >>> z.oindex[[0, 2], :]  # select first and third rows
   array([[ 0,  1,  2,  3,  4],
          [10, 11, 12, 13, 14]])
   >>> z.oindex[:, [1, 3]]  # select second and fourth columns
   array([[ 1,  3],
          [ 6,  8],
          [11, 13]])
   >>> z.oindex[[0, 2], [1, 3]]  # select rows [0, 2] and columns [1, 4]
   array([[ 1,  3],
          [11, 13]])
   >>> z.oindex[[0, 2], [1, 3]] = [[-1, -2], [-3, -4]]
   >>> z[:]
   array([[ 0, -1,  2, -2,  4],
          [ 5,  6,  7,  8,  9],
          [10, -3, 12, -4, 14]])

Any combination of integer, slice, 1D integer array and/or 1D Boolean array can
be used for orthogonal indexing.

If the index contains at most one iterable, and otherwise contains only slices and integers,
orthogonal indexing is also available directly on the array::

   >>> data = np.arange(15).reshape(3, 5)
   >>> z = zarr.create_array(store='data/example-16.zarr', shape=data.shape, dtype=data.dtype)
   >>> z[:] = data
   >>> np.all(z.oindex[[0, 2], :] == z[[0, 2], :])
   np.True_

Block Indexing
~~~~~~~~~~~~~~

Zarr also support block indexing, which allows selections of whole chunks based on their
logical indices along each dimension of an array. For example, this allows selecting
a subset of chunk aligned rows and/or columns from a 2-dimensional array. E.g.::

   >>> data = np.arange(100).reshape(10, 10)
   >>> z = zarr.create_array(store='data/example-17.zarr', shape=data.shape, dtype=data.dtype, chunks=(3, 3))
   >>> z[:] = data

Retrieve items by specifying their block coordinates::

   >>> z.get_block_selection(1)
   array([[30, 31, 32, 33, 34, 35, 36, 37, 38, 39],
          [40, 41, 42, 43, 44, 45, 46, 47, 48, 49],
          [50, 51, 52, 53, 54, 55, 56, 57, 58, 59]])

Equivalent slicing::

   >>> z[3:6]
   array([[30, 31, 32, 33, 34, 35, 36, 37, 38, 39],
          [40, 41, 42, 43, 44, 45, 46, 47, 48, 49],
          [50, 51, 52, 53, 54, 55, 56, 57, 58, 59]])

For convenience, the block selection functionality is also available via the
`blocks` property, e.g.::

   >>> z.blocks[1]
   array([[30, 31, 32, 33, 34, 35, 36, 37, 38, 39],
          [40, 41, 42, 43, 44, 45, 46, 47, 48, 49],
          [50, 51, 52, 53, 54, 55, 56, 57, 58, 59]])

Block index arrays may be multidimensional to index multidimensional arrays.
For example::

   >>> z.blocks[0, 1:3]
   array([[ 3,  4,  5,  6,  7,  8],
          [13, 14, 15, 16, 17, 18],
          [23, 24, 25, 26, 27, 28]])

Data can also be modified. Let's start by a simple 2D array::

   >>> z = zarr.create_array(store='data/example-18.zarr', shape=(6, 6), dtype=int, chunks=(2, 2))

Set data for a selection of items::

   >>> z.set_block_selection((1, 0), 1)
   >>> z[...]
   array([[0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0],
          [1, 1, 0, 0, 0, 0],
          [1, 1, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0],
          [0, 0, 0, 0, 0, 0]])

For convenience, this functionality is also available via the ``blocks`` property.
E.g.::

   >>> z.blocks[:, 2] = 7
   >>> z[...]
   array([[0, 0, 0, 0, 7, 7],
          [0, 0, 0, 0, 7, 7],
          [1, 1, 0, 0, 7, 7],
          [1, 1, 0, 0, 7, 7],
          [0, 0, 0, 0, 7, 7],
          [0, 0, 0, 0, 7, 7]])

Any combination of integer and slice can be used for block indexing::

   >>> z.blocks[2, 1:3]
   array([[0, 0, 7, 7],
          [0, 0, 7, 7]])
   >>>
   >>> root = zarr.create_group('data/example-19.zarr')
   >>> foo = root.create_array(name='foo', shape=(1000, 100), chunks=(10, 10), dtype='float32')
   >>> bar = root.create_array(name='foo/bar', shape=(100,), dtype='int32')
   >>> foo[:, :] = np.random.random((1000, 100))
   >>> bar[:] = np.arange(100)
   >>> root.tree()
   /
   └── foo (1000, 100) float32
   <BLANKLINE>

.. _user-guide-sharding:

Sharding
--------

Using small chunk shapes in very large arrays can lead to a very large number of chunks.
This can become a performance issue for file systems and object storage.
With Zarr format 3, a new sharding feature has been added to address this issue.

With sharding, multiple chunks can be stored in a single storage object (e.g. a file).
Within a shard, chunks are compressed and serialized separately.
This allows individual chunks to be read independently.
However, when writing data, a full shard must be written in one go for optimal
performance and to avoid concurrency issues.
That means that shards are the units of writing and chunks are the units of reading.
Users need to configure the chunk and shard shapes accordingly.

Sharded arrays can be created by providing the ``shards`` parameter to :func:`zarr.create_array`.

  >>> a = zarr.create_array('data/example-20.zarr', shape=(10000, 10000), shards=(1000, 1000), chunks=(100, 100), dtype='uint8')
  >>> a[:] = (np.arange(10000 * 10000) % 256).astype('uint8').reshape(10000, 10000)
  >>> a.info_complete()
  Type               : Array
  Zarr format        : 3
  Data type          : DataType.uint8
  Shape              : (10000, 10000)
  Shard shape        : (1000, 1000)
  Chunk shape        : (100, 100)
  Order              : C
  Read-only          : False
  Store type         : LocalStore
  Filters            : ()
  Serializer         : BytesCodec(endian=<Endian.little: 'little'>)
  Compressors        : (ZstdCodec(level=0, checksum=False),)
  No. bytes          : 100000000 (95.4M)
  No. bytes stored   : 3981552
  Storage ratio      : 25.1
  Shards Initialized : 100

In this example a shard shape of (1000, 1000) and a chunk shape of (100, 100) is used.
This means that 10*10 chunks are stored in each shard, and there are 10*10 shards in total.
Without the ``shards`` argument, there would be 10,000 chunks stored as individual files.

Missing features in 3.0
-----------------------


The following features have not been ported to 3.0 yet.

.. _user-guide-objects:

Object arrays
~~~~~~~~~~~~~

See the Zarr-Python 2 documentation on `Object arrays <https://zarr.readthedocs.io/en/support-v2/tutorial.html#object-arrays>`_ for more details.

.. _user-guide-strings:

Fixed-length string arrays
~~~~~~~~~~~~~~~~~~~~~~~~~~

See the Zarr-Python 2 documentation on `Fixed-length string arrays <https://zarr.readthedocs.io/en/support-v2/tutorial.html#string-arrays>`_ for more details.

.. _user-guide-datetime:

Datetime and Timedelta arrays
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

See the Zarr-Python 2 documentation on `Datetime and Timedelta <https://zarr.readthedocs.io/en/support-v2/tutorial.html#datetimes-and-timedeltas>`_ for more details.

.. _user-guide-copy:

Copying and migrating data
~~~~~~~~~~~~~~~~~~~~~~~~~~

See the Zarr-Python 2 documentation on `Copying and migrating data <https://zarr.readthedocs.io/en/support-v2/tutorial.html#copying-migrating-data>`_ for more details.