Test if an array is broadcastable to a shape?

Question

What is the best way to test whether an array can be broadcast to a given shape?

The \"pythonic\" approach of trying doesn\'t work for my case, because the

Answer 1

To generalize this to arbitrarily many shapes, you can do so as follows:

def is_broadcast_compatible(*shapes):
    if len(shapes) < 2:
        return True
    else:
        for dim in zip(*[shape[::-1] for shape in shapes]):
            if len(set(dim).union({1})) <= 2:
                pass
            else:
                return False
        return True

The corresponding test case is as follows:

import unittest


class TestBroadcastCompatibility(unittest.TestCase):
    def check_true(self, *shapes):
        self.assertTrue(is_broadcast_compatible(*shapes), msg=shapes)

    def check_false(self, *shapes):
        self.assertFalse(is_broadcast_compatible(*shapes), msg=shapes)

    def test(self):
        self.check_true((1, 2, 3), (1, 2, 3))
        self.check_true((3, 1, 3), (3, 3, 3))
        self.check_true((1,), (2,), (2,))

        self.check_false((1, 2, 3), (1, 2, 2))
        self.check_false((1, 2, 3), (1, 2, 3, 4))
        self.check_false((1,), (2,), (3,))