numpy testing assert array NOT equal

Question

We have numpy.testing.assert_array_equal to assert that two arrays are equal.

But what is the best way to do numpy.testing.assert_array_not_equal, that is, to make sure that two arrays are NOT equal?

Asked By: Hallgeir Wilhelmsen

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Source

Answer 1

I don’t think there is anything built directly into the NumPy testing framework but you could just use:

np.any(np.not_equal(a1,a2))

and assert true with the built in unittest framework or check with NumPy as assert_equal to True e.g.

np.testing.assert_equal(np.any(np.not_equal(a,a)), True)

Answered By: Mark

Answer 2

If you want to use specifically NumPy testing, then you can use numpy.testing.assert_array_equal together with numpy.testing.assert_raises for the opposite result. For example:

assert_raises(AssertionError, assert_array_equal, array_1, array_2)

Also there is numpy.testing.utils.assert_array_compare (it is used by numpy.testing.assert_array_equal), but I don’t see it documented anywhere, so use with caution. This one will check that every element is different, so I guess this is not your use case:

import operator

assert_array_compare(operator.__ne__, array_1, array_2)

Answered By: Eswcvlad

Answer 3

Not sure why this hasn’t been posted, may be I didn’t understand the question properly, but what about:

assert not np.array_equal(array1 , array2)

Any reason why you would like to keep it exclusively in the testing module of numpy?

Answered By: Jose Sergio Hleap

Answer 4

Cleaner syntax to @Eswcvlad’s answer:

import numpy as np

with np.testing.assert_raises(AssertionError):
    np.testing.assert_array_equal(expected, actual)

Answered By: Mikhail

Answer 5

Perhaps you usually want to test if something is almost equal (considering decimal precision) and consequently want to test if something is NOT almost equal in some cases. Building on @Mikhail answer (and also using pytest.raises) this would give:

import numpy as np
import pytest
 
with pytest.raises(AssertionError):
   np.testing.assert_almost_equal(...)

Answered By: Martin Alexandersson

Answer 6

Improving the accepted answer, we can make assert_array_not_equal as follows

from numpy.testing import assert_array_equal, assert_raises


def assert_array_not_equal(x, y):
    return assert_raises(AssertionError, assert_array_equal, x, y)

Answered By: Muhammad Yasirroni

numpy testing assert array NOT equal

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