NumPy

numpy.savez

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

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

If arguments are passed in with no keywords, the corresponding variable names, in the .npz file, are ‘arr_0’, ‘arr_1’, etc. If keyword arguments are given, the corresponding variable names, in the .npz file will match the keyword names.

Parameters
filestr or file

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. Since it is not possible for Python to know the names of the arrays outside savez, the arrays will be saved with names “arr_0”, “arr_1”, and so on. These arguments can be any expression.

kwdsKeyword arguments, optional

Arrays to save to the file. Arrays will be saved in the file with the keyword names.

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.

When saving dictionaries, the dictionary keys become filenames inside the ZIP archive. Therefore, keys should be valid filenames. E.g., avoid keys that begin with / or contain ..

Examples

>>> 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 here 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])

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