bundles / scipy latest / scipy / io / _fast_matrix_market / mmwrite

function

`scipy.io._fast_matrix_market:mmwrite`

source: build-install/usr/lib/python3.14/site-packages/scipy/io/_fast_matrix_market/__init__.py:413

Signature

def mmwrite(target, a, comment = None, field = None, precision = None, symmetry = AUTO)

Summary

Writes the sparse or dense array a to Matrix Market file-like target.

Parameters

target : str or file-like: Matrix Market filename (extension .mtx) or open file-like object.
a : array like: Sparse or dense 2-D array.
comment : str, optional: Comments to be prepended to the Matrix Market file.
field : None or str, optional: Either 'real', 'complex', 'pattern', or 'integer'.
precision : None or int, optional: Number of digits to display for real or complex values.
symmetry : None or str, optional: Either 'AUTO', 'general', 'symmetric', 'skew-symmetric', or 'hermitian'. If symmetry is None the symmetry type of 'a' is determined by its values. If symmetry is 'AUTO' the symmetry type of 'a' is either determined or set to 'general', at mmwrite's discretion.

Notes

Examples

from io import BytesIO
import numpy as np
from scipy.sparse import coo_array
from scipy.io import mmwrite

✓

Write a small NumPy array to a matrix market file. The file will be written in the ``'array'`` format.

a = np.array([[1.0, 0, 0, 0], [0, 2.5, 0, 6.25]])
target = BytesIO()
mmwrite(target, a)

✓

print(target.getvalue().decode('latin1'))

✗

%%MatrixMarket matrix array real general
%
2 4
1
0
0
2.5
0
0
0
6.25

Add a comment to the output file, and set the precision to 3.

target = BytesIO()
mmwrite(target, a, comment='\n Some test data.\n', precision=3)

✓

print(target.getvalue().decode('latin1'))

✗

%%MatrixMarket matrix array real general
%
% Some test data.
%
2 4
1.00e+00
0.00e+00
0.00e+00
2.50e+00
0.00e+00
0.00e+00
0.00e+00
6.25e+00

Convert to a sparse matrix before calling ``mmwrite``. This will result in the output format being ``'coordinate'`` rather than ``'array'``.

target = BytesIO()
mmwrite(target, coo_array(a), precision=3)

✓

print(target.getvalue().decode('latin1'))

✗

%%MatrixMarket matrix coordinate real general
%
2 4 3
1 1 1.00e+00
2 2 2.50e+00
2 4 6.25e+00

Write a complex Hermitian array to a matrix market file. Note that only six values are actually written to the file; the other values are implied by the symmetry.

z = np.array([[3, 1+2j, 4-3j], [1-2j, 1, -5j], [4+3j, 5j, 2.5]])
z

✓

array([[ 3. +0.j,  1. +2.j,  4. -3.j],
       [ 1. -2.j,  1. +0.j, -0. -5.j],
       [ 4. +3.j,  0. +5.j,  2.5+0.j]])

target = BytesIO()
mmwrite(target, z, precision=2)

✓

print(target.getvalue().decode('latin1'))

✗

%%MatrixMarket matrix array complex hermitian
%
3 3
3.0e+00 0.0e+00
1.0e+00 -2.0e+00
4.0e+00 3.0e+00
1.0e+00 0.0e+00
0.0e+00 5.0e+00
2.5e+00 0.0e+00

This method is threaded. The default number of threads is equal to the number of CPUs in the system. Use `threadpoolctl <https://github.com/joblib/threadpoolctl>`_ to override:

import threadpoolctl

⚠

Traceback (most recent call last):
  File "<doctest scipy.io._fast_matrix_market:mmwrite[0]>", line 1, in <module>
    import threadpoolctl
ModuleNotFoundError: No module named 'threadpoolctl'

target = BytesIO()

✓

with threadpoolctl.threadpool_limits(limits=2):
    mmwrite(target, a)

⚠

Traceback (most recent call last):
  File "<doctest scipy.io._fast_matrix_market:mmwrite[0]>", line 1, in <module>
    with threadpoolctl.threadpool_limits(limits=2):
         ^^^^^^^^^^^^^
NameError: name 'threadpoolctl' is not defined

`scipy.io._fast_matrix_market:mmwrite`

Signature

Summary

Parameters

Notes

Examples

Aliases

Referenced by

This package