al of the upper triangle.
format : string
    Sparse format of the result, e.g. format="csr", etc.

Returns
-------
L : sparse array or matrix
    Upper triangular portion of A in sparse format.
    Sparse array if A is a sparse array, otherwise matrix.

See Also
--------
tril : lower triangle in sparse format

Examples
--------
>>> from scipy.sparse import csr_array, triu
>>> A = csr_array([[1, 2, 0, 0, 3], [4, 5, 0, 6, 7], [0, 0, 8, 9, 0]],
...                dtype='int32')
>>> A.toarray()
array([[1, 2, 0, 0, 3],
       [4, 5, 0, 6, 7],
       [0, 0, 8, 9, 0]], dtype=int32)
>>> triu(A).toarray()
array([[1, 2, 0, 0, 3],
       [0, 5, 0, 6, 7],
       [0, 0, 8, 9, 0]], dtype=int32)
>>> triu(A).nnz
8
>>> triu(A, k=1).toarray()
array([[0, 2, 0, 0, 3],
       [0, 0, 0, 6, 7],
       [0, 0, 0, 9, 0]], dtype=int32)
>>> triu(A, k=-1).toarray()
array([[1, 2, 0, 0, 3],
       [4, 5, 0, 6, 7],
       [0, 0, 8, 9, 0]], dtype=int32)
>>> triu(A, format='csc')
<Compressed Sparse Column sparse array of dtype 'int32'
    with 8 stored elements and shape (3, 5)>

Fr