Array creation (zarr.creation
)¶
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zarr.creation.
create
(shape, chunks, dtype=None, compression='default', compression_opts=None, fill_value=None, order='C', store=None, synchronizer=None, overwrite=False)¶ Create an array.
Parameters: shape : int or tuple of ints
Array shape.
chunks : int or tuple of ints
Chunk shape.
dtype : string or dtype, optional
NumPy dtype.
compression : string, optional
Name of primary compression library, e.g., ‘blosc’, ‘zlib’, ‘bz2’, ‘lzma’.
compression_opts : object, optional
Options to primary compressor. E.g., for blosc, provide a dictionary with keys ‘cname’, ‘clevel’ and ‘shuffle’.
fill_value : object
Default value to use for uninitialised portions of the array.
order : {‘C’, ‘F’}, optional
Memory layout to be used within each chunk.
store : MutableMapping, optional
Array storage. If not provided, a Python dict will be used, meaning array data will be stored in memory.
synchronizer : zarr.sync.ArraySynchronizer, optional
Array synchronizer.
overwrite : bool, optional
If True, delete all pre-existing data in store before creating the array.
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, chunks=(1000, 1000), order=C) compression: blosc; compression_opts: {'clevel': 5, 'cname': 'lz4', 'shuffle': 1} nbytes: 762.9M; nbytes_stored: 316; ratio: 2531645.6; initialized: 0/100 store: builtins.dict
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zarr.creation.
empty
(shape, chunks, dtype=None, compression='default', compression_opts=None, order='C', store=None, synchronizer=None)¶ 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.
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zarr.creation.
zeros
(shape, chunks, dtype=None, compression='default', compression_opts=None, order='C', store=None, synchronizer=None)¶ Create an array, with zero being used as the default value for uninitialised 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, chunks=(1000, 1000), order=C) compression: blosc; compression_opts: {'clevel': 5, 'cname': 'lz4', 'shuffle': 1} nbytes: 762.9M; nbytes_stored: 313; ratio: 2555910.5; initialized: 0/100 store: builtins.dict >>> z[:2, :2] array([[ 0., 0.], [ 0., 0.]])
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zarr.creation.
ones
(shape, chunks, dtype=None, compression='default', compression_opts=None, order='C', store=None, synchronizer=None)¶ Create an array, with one being used as the default value for uninitialised 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, chunks=(1000, 1000), order=C) compression: blosc; compression_opts: {'clevel': 5, 'cname': 'lz4', 'shuffle': 1} nbytes: 762.9M; nbytes_stored: 313; ratio: 2555910.5; initialized: 0/100 store: builtins.dict >>> z[:2, :2] array([[ 1., 1.], [ 1., 1.]])
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zarr.creation.
full
(shape, chunks, fill_value, dtype=None, compression='default', compression_opts=None, order='C', store=None, synchronizer=None)¶ Create an array, with fill_value being used as the default value for uninitialised 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, chunks=(1000, 1000), order=C) compression: blosc; compression_opts: {'clevel': 5, 'cname': 'lz4', 'shuffle': 1} nbytes: 762.9M; nbytes_stored: 314; ratio: 2547770.7; initialized: 0/100 store: builtins.dict >>> z[:2, :2] array([[ 42., 42.], [ 42., 42.]])
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zarr.creation.
array
(data, chunks=None, dtype=None, compression='default', compression_opts=None, fill_value=None, order='C', store=None, synchronizer=None)¶ 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, chunks=(1000, 1000), order=C) compression: blosc; compression_opts: {'clevel': 5, 'cname': 'lz4', 'shuffle': 1} nbytes: 762.9M; nbytes_stored: 17.1M; ratio: 44.7; initialized: 100/100 store: builtins.dict
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zarr.creation.
open
(path, mode='a', shape=None, chunks=None, dtype=None, compression='default', compression_opts=None, fill_value=0, order='C', synchronizer=None)¶ Open an array stored in a directory on the file system.
Parameters: path : string
Path to directory in which to store the array.
mode : {‘r’, ‘r+’, ‘a’, ‘w’, ‘w-‘}
Persistence mode: ‘r’ means readonly (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
Array shape.
chunks : int or tuple of ints
Chunk shape.
dtype : string or dtype, optional
NumPy dtype.
compression : string, optional
Name of primary compression library, e.g., ‘blosc’, ‘zlib’, ‘bz2’, ‘lzma’.
compression_opts : object, optional
Options to primary compressor. E.g., for blosc, provide a dictionary with keys ‘cname’, ‘clevel’ and ‘shuffle’.
fill_value : object
Default value to use for uninitialised portions of the array.
order : {‘C’, ‘F’}, optional
Memory layout to be used within each chunk.
synchronizer : zarr.sync.ArraySynchronizer, optional
Array synchronizer.
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('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, chunks=(1000, 1000), order=C) compression: blosc; compression_opts: {'clevel': 5, 'cname': 'lz4', 'shuffle': 1} nbytes: 762.9M; nbytes_stored: 24.8M; ratio: 30.8; initialized: 100/100 store: zarr.storage.DirectoryStore >>> z2 = zarr.open('example.zarr', mode='r') >>> z2 zarr.core.Array((10000, 10000), float64, chunks=(1000, 1000), order=C) compression: blosc; compression_opts: {'clevel': 5, 'cname': 'lz4', 'shuffle': 1} nbytes: 762.9M; nbytes_stored: 24.8M; ratio: 30.8; initialized: 100/100 store: zarr.storage.DirectoryStore >>> np.all(z1[:] == z2[:]) True
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zarr.creation.
empty_like
(a, shape=None, chunks=None, dtype=None, compression=None, compression_opts=None, order=None, store=None, synchronizer=None)¶ Create an empty array like a.
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zarr.creation.
zeros_like
(a, shape=None, chunks=None, dtype=None, compression=None, compression_opts=None, order=None, store=None, synchronizer=None)¶ Create an array of zeros like a.
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zarr.creation.
ones_like
(a, shape=None, chunks=None, dtype=None, compression=None, compression_opts=None, order=None, store=None, synchronizer=None)¶ Create an array of ones like a.
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zarr.creation.
full_like
(a, shape=None, chunks=None, fill_value=None, dtype=None, compression=None, compression_opts=None, order=None, store=None, synchronizer=None)¶ Create a filled array like a.
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zarr.creation.
open_like
(a, path, mode='a', shape=None, chunks=None, dtype=None, compression=None, compression_opts=None, fill_value=None, order=None, synchronizer=None)¶ Open a persistent array like a.