numpy.savez#

numpy.savez(file, *args, **kwds)[source]#

Save several arrays into a single file in uncompressed .npz format.

Provide arrays as keyword arguments to store them under the corresponding name in the output file: savez(fn, x=x, y=y).

If arrays are specified as positional arguments, i.e., savez(fn, x, y), their names will be arr_0, arr_1, etc.

Parameters:

filefile, str, or pathlib.Path: Either the filename (string) or an open file (file-like object) where the data will be saved. If file is a string or a Path, the .npz extension will be appended to the filename if it is not already there.
argsArguments, optional: Arrays to save to the file. Please use keyword arguments (see kwds below) to assign names to arrays. Arrays specified as args will be named “arr_0”, “arr_1”, and so on.
kwdsKeyword arguments, optional: Arrays to save to the file. Each array will be saved to the output file with its corresponding keyword name.

Returns:

None

See also

save: Save a single array to a binary file in NumPy format.
savetxt: Save an array to a file as plain text.
savez_compressed: Save several arrays into a compressed .npz archive

Notes

The .npz file format is a zipped archive of files named after the variables they contain. The archive is not compressed and each file in the archive contains one variable in .npy format. For a description of the .npy format, see numpy.lib.format.

When opening the saved .npz file with load a NpzFile object is returned. This is a dictionary-like object which can be queried for its list of arrays (with the .files attribute), and for the arrays themselves.

Keys passed in kwds are used as filenames inside the ZIP archive. Therefore, keys should be valid filenames; e.g., avoid keys that begin with / or contain ..

When naming variables with keyword arguments, it is not possible to name a variable file, as this would cause the file argument to be defined twice in the call to savez.

Examples

>>> import numpy as np
>>> from tempfile import TemporaryFile
>>> outfile = TemporaryFile()
>>> x = np.arange(10)
>>> y = np.sin(x)

Using savez with *args, the arrays are saved with default names.

>>> np.savez(outfile, x, y)
>>> _ = outfile.seek(0) # Only needed to simulate closing & reopening file
>>> npzfile = np.load(outfile)
>>> npzfile.files
['arr_0', 'arr_1']
>>> npzfile['arr_0']
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

Using savez with **kwds, the arrays are saved with the keyword names.

>>> outfile = TemporaryFile()
>>> np.savez(outfile, x=x, y=y)
>>> _ = outfile.seek(0)
>>> npzfile = np.load(outfile)
>>> sorted(npzfile.files)
['x', 'y']
>>> npzfile['x']
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])