Array creation (zarr.creation
)¶
-
zarr.creation.
create
(shape, chunks=True, dtype=None, compressor='default', fill_value=0, order='C', store=None, synchronizer=None, overwrite=False, path=None, chunk_store=None, filters=None, cache_metadata=True, cache_attrs=True, read_only=False, object_codec=None, **kwargs)[source]¶ Create an array.
Parameters: - shape : int or tuple of ints
Array shape.
- chunks : int or tuple of ints, optional
Chunk shape. If True, will be guessed from shape and dtype. If False, will be set to shape, i.e., single chunk for the whole array. If an int, the chunk size in each dimension will be given by the value of chunks. Default is True.
- dtype : string or dtype, optional
NumPy dtype.
- compressor : Codec, optional
Primary compressor.
- fill_value : object
Default value to use for uninitialized portions of the array.
- order : {‘C’, ‘F’}, optional
Memory layout to be used within each chunk.
- store : MutableMapping or string
Store or path to directory in file system or name of zip file.
- synchronizer : object, optional
Array synchronizer.
- overwrite : bool, optional
If True, delete all pre-existing data in store at path before creating the array.
- path : string, optional
Path under which array is stored.
- chunk_store : MutableMapping, optional
Separate storage for chunks. If not provided, store will be used for storage of both chunks and metadata.
- filters : sequence of Codecs, optional
Sequence of filters to use to encode chunk data prior to compression.
- cache_metadata : bool, optional
If True, array configuration metadata will be cached for the lifetime of the object. If False, array metadata will be reloaded prior to all data access and modification operations (may incur overhead depending on storage and data access pattern).
- cache_attrs : bool, optional
If True (default), user attributes will be cached for attribute read operations. If False, user attributes are reloaded from the store prior to all attribute read operations.
- read_only : bool, optional
True if array should be protected against modification.
- object_codec : Codec, optional
A codec to encode object arrays, only needed if dtype=object.
Returns: - z : zarr.core.Array
Examples
Create an array with default settings:
>>> import zarr >>> z = zarr.create((10000, 10000), chunks=(1000, 1000)) >>> z <zarr.core.Array (10000, 10000) float64>
Create an array with different some different configuration options:
>>> from numcodecs import Blosc >>> compressor = Blosc(cname='zstd', clevel=1, shuffle=Blosc.BITSHUFFLE) >>> z = zarr.create((10000, 10000), chunks=(1000, 1000), dtype='i1', order='F', ... compressor=compressor) >>> z <zarr.core.Array (10000, 10000) int8>
To create an array with object dtype requires a filter that can handle Python object encoding, e.g., MsgPack or Pickle from numcodecs:
>>> from numcodecs import MsgPack >>> z = zarr.create((10000, 10000), chunks=(1000, 1000), dtype=object, ... object_codec=MsgPack()) >>> z <zarr.core.Array (10000, 10000) object>
Example with some filters, and also storing chunks separately from metadata:
>>> from numcodecs import Quantize, Adler32 >>> store, chunk_store = dict(), dict() >>> z = zarr.create((10000, 10000), chunks=(1000, 1000), dtype='f8', ... filters=[Quantize(digits=2, dtype='f8'), Adler32()], ... store=store, chunk_store=chunk_store) >>> z <zarr.core.Array (10000, 10000) float64>
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zarr.creation.
empty
(shape, **kwargs)[source]¶ Create an empty array.
For parameter definitions see
zarr.creation.create()
.Notes
The contents of an empty Zarr array are not defined. On attempting to retrieve data from an empty Zarr array, any values may be returned, and these are not guaranteed to be stable from one access to the next.
-
zarr.creation.
zeros
(shape, **kwargs)[source]¶ Create an array, with zero being used as the default value for uninitialized portions of the array.
For parameter definitions see
zarr.creation.create()
.Examples
>>> import zarr >>> z = zarr.zeros((10000, 10000), chunks=(1000, 1000)) >>> z <zarr.core.Array (10000, 10000) float64> >>> z[:2, :2] array([[0., 0.], [0., 0.]])
-
zarr.creation.
ones
(shape, **kwargs)[source]¶ Create an array, with one being used as the default value for uninitialized portions of the array.
For parameter definitions see
zarr.creation.create()
.Examples
>>> import zarr >>> z = zarr.ones((10000, 10000), chunks=(1000, 1000)) >>> z <zarr.core.Array (10000, 10000) float64> >>> z[:2, :2] array([[1., 1.], [1., 1.]])
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zarr.creation.
full
(shape, fill_value, **kwargs)[source]¶ Create an array, with fill_value being used as the default value for uninitialized portions of the array.
For parameter definitions see
zarr.creation.create()
.Examples
>>> import zarr >>> z = zarr.full((10000, 10000), chunks=(1000, 1000), fill_value=42) >>> z <zarr.core.Array (10000, 10000) float64> >>> z[:2, :2] array([[42., 42.], [42., 42.]])
-
zarr.creation.
array
(data, **kwargs)[source]¶ Create an array filled with data.
The data argument should be a NumPy array or array-like object. For other parameter definitions see
zarr.creation.create()
.Examples
>>> import numpy as np >>> import zarr >>> a = np.arange(100000000).reshape(10000, 10000) >>> z = zarr.array(a, chunks=(1000, 1000)) >>> z <zarr.core.Array (10000, 10000) int64>
-
zarr.creation.
open_array
(store=None, mode='a', shape=None, chunks=True, dtype=None, compressor='default', fill_value=0, order='C', synchronizer=None, filters=None, cache_metadata=True, cache_attrs=True, path=None, object_codec=None, chunk_store=None, storage_options=None, **kwargs)[source]¶ Open an array using file-mode-like semantics.
Parameters: - store : MutableMapping or string, optional
Store or path to directory in file system or name of zip file.
- mode : {‘r’, ‘r+’, ‘a’, ‘w’, ‘w-‘}, optional
Persistence mode: ‘r’ means read only (must exist); ‘r+’ means read/write (must exist); ‘a’ means read/write (create if doesn’t exist); ‘w’ means create (overwrite if exists); ‘w-‘ means create (fail if exists).
- shape : int or tuple of ints, optional
Array shape.
- chunks : int or tuple of ints, optional
Chunk shape. If True, will be guessed from shape and dtype. If False, will be set to shape, i.e., single chunk for the whole array. If an int, the chunk size in each dimension will be given by the value of chunks. Default is True.
- dtype : string or dtype, optional
NumPy dtype.
- compressor : Codec, optional
Primary compressor.
- fill_value : object, optional
Default value to use for uninitialized portions of the array.
- order : {‘C’, ‘F’}, optional
Memory layout to be used within each chunk.
- synchronizer : object, optional
Array synchronizer.
- filters : sequence, optional
Sequence of filters to use to encode chunk data prior to compression.
- cache_metadata : bool, optional
If True, array configuration metadata will be cached for the lifetime of the object. If False, array metadata will be reloaded prior to all data access and modification operations (may incur overhead depending on storage and data access pattern).
- cache_attrs : bool, optional
If True (default), user attributes will be cached for attribute read operations. If False, user attributes are reloaded from the store prior to all attribute read operations.
- path : string, optional
Array path within store.
- object_codec : Codec, optional
A codec to encode object arrays, only needed if dtype=object.
- chunk_store : MutableMapping or string, optional
Store or path to directory in file system or name of zip file.
- storage_options : dict
If using an fsspec URL to create the store, these will be passed to the backend implementation. Ignored otherwise.
Returns: - z : zarr.core.Array
Notes
There is no need to close an array. Data are automatically flushed to the file system.
Examples
>>> import numpy as np >>> import zarr >>> z1 = zarr.open_array('data/example.zarr', mode='w', shape=(10000, 10000), ... chunks=(1000, 1000), fill_value=0) >>> z1[:] = np.arange(100000000).reshape(10000, 10000) >>> z1 <zarr.core.Array (10000, 10000) float64> >>> z2 = zarr.open_array('data/example.zarr', mode='r') >>> z2 <zarr.core.Array (10000, 10000) float64 read-only> >>> np.all(z1[:] == z2[:]) True