NumPy has the efficient function/method `nonzero()`

to identify the indices of non-zero elements in an `ndarray`

object. What is the most efficient way to obtain the indices of the elements that *do* have a value of zero?

numpy.where() is my favorite.

>>> x = numpy.array([1,0,2,0,3,0,4,5,6,7,8]) >>> numpy.where(x == 0)[0] array([1, 3, 5])

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