# numpy.flatnonzero

numpy.flatnonzero(a)

  Return indices that are non-zero in the flattened version of a.

  This is equivalent to `np.nonzero(np.ravel(a))[0]`.

  Parameters:
    a array_like

      Input data.

  Returns:
    res ndarray

      Output array, containing the indices of the elements of `a.ravel()` that are non-zero.

  See also

  `nonzero`

    Return the indices of the non-zero elements of the input array.

  `ravel`

    Return a 1-D array containing the elements of the input array.

  Examples

      >>> x = np.arange(-2, 3)
      >>> x
      array([-2, -1,  0,  1,  2])
      >>> np.flatnonzero(x)
      array([0, 1, 3, 4])

  Use the indices of the non-zero elements as an index array to extract these elements:

      >>> x.ravel()[np.flatnonzero(x)]
      array([-2, -1,  1,  2])