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# numpy.flatnonzero

`numpy.``flatnonzero`(a)

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

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

  Parameters: | a : ndarray Input array.
  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])