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# numpy.tril

`numpy.``tril`(m, k=0)

  Lower triangle of an array.

  Return a copy of an array with elements above the k-th diagonal zeroed.

  Parameters : | m : array_like, shape (M, N) Input array. k : int, optional Diagonal above which to zero elements. k = 0 (the default) is the main diagonal, k < 0 is below it and k > 0 is above.
  Returns : | tril : ndarray, shape (M, N) Lower triangle of m, of same shape and data-type as m.

  See also

  `triu`
    same thing, only for the upper triangle

  Examples

      >>> np.tril([[1,2,3],[4,5,6],[7,8,9],[10,11,12]], -1)
      array([[ 0,  0,  0],
             [ 4,  0,  0],
             [ 7,  8,  0],
             [10, 11, 12]])