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# numpy.core.defchararray.index

`numpy.core.defchararray.``index`(a, sub, start=0, end=None)

  Like `find`, but raises ValueError when the substring is not found.

  Calls str.index element-wise.

  Parameters: | a : array_like of str or unicode sub : str or unicode start, end : int, optional
  Returns: | out : ndarray Output array of ints. Returns -1 if sub is not found.

  See also

  `find`, `str.find`