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

If you just want to avoid materializing an array with a given shape, you can use as_strided:

import numpy as np
from numpy.lib.stride_tricks import as_strided

def is_broadcastable(shp1, shp2):
    x = np.array([1])
    a = as_strided(x, shape=shp1, strides=[0] * len(shp1))
    b = as_strided(x, shape=shp2, strides=[0] * len(shp2))
    try:
        c = np.broadcast_arrays(a, b)
        return True
    except ValueError:
        return False

is_broadcastable((1000, 1000, 1000), (1000, 1, 1000))  # True
is_broadcastable((1000, 1000, 1000), (3,))  # False

This is memory efficient, since a and b are both backed by a single record