In [916]: alist=[sparse.random(1,10,.2, format='csr') for _ in range(3)]
In [917]: alist
Out[917]:
[<1x10 sparse matrix of type '<class 'numpy.float64'>'
    with 2 stored elements in Compressed Sparse Row format>,
 <1x10 sparse matrix of type '<class 'numpy.float64'>'
    with 2 stored elements in Compressed Sparse Row format>,
 <1x10 sparse matrix of type '<class 'numpy.float64'>'
    with 2 stored elements in Compressed Sparse Row format>]

In [918]: sparse.vstack(alist)
Out[918]:
<3x10 sparse matrix of type '<class 'numpy.float64'>'
    with 6 stored elements in Compressed Sparse Row format>

In [919]: np.array(alist)
Out[919]:
array([ <1x10 sparse matrix of type '<class 'numpy.float64'>'
    with 2 stored elements in Compressed Sparse Row format>,
       <1x10 sparse matrix of type '<class 'numpy.float64'>'
    with 2 stored elements in Compressed Sparse Row format>,
       <1x10 sparse matrix of type '<class 'numpy.float64'>'
    with 2 stored elements in Compressed Sparse Row format>], dtype=object)

In [920]: np.array(alist, float)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-920-52d4689fa7b3> in <module>()
----> 1 np.array(alist, float)

ValueError: setting an array element with a sequence.