[Python] Breadth-first search on numpy array for consecutive adjacent zeroes

I have a numpy array that looks like the following:

arr = np.array([[-1, -1, -1, 0, -1]
[ -1, -1, -1, 0, -1]
[ -1, 0, -1, -1, 0]
[ -1, 0, -1, -1, -1]
[ -1, -1, -1, -1, 0]])


I want each consecutive region marked with a 0 (including diagonals) to be changed to a different value, such that my array would end up looking like this:

arr = np.array([[ -1, -1, -1, 1, -1]
[ -1, -1, -1, 1, -1]
[ -1, 2, -1, -1, 1]
[ -1, 2, -1, -1, -1]
[ -1, -1, -1, -1, 3]])


One way of doing this could be through a breadth-first search. Is there any convenient way to do this, or is there an easier method available?

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