# span of a matrixspace

given a matrix subspace of sparse matrices over a ring Q

M=MatrixSpace(Q,1000,1000, sparse=True)

I need a way to define the subspace N of M given a list of matrices of M

I tried to turn matrices into lists and use the VectorSpace category, however my matrices are sparse matrices, and this takes very long

```
def lista(A): #converts a matrix into a list
return A.list()
def coor(P): # for the determined base B, it gives the coordinate vector of a matrix P[0]
A=base(P[1][1])
k=len(P[1][1])
V=VectorSpace(Q,2**(2*k), sparse=True) #I would like to work with MatrixSpace instead
B=[] #this will be my basis
for i in range(len(A)):
a=A[i][0]
B.append(V(lista(a)))
W=W=V.span_of_basis(B) #I dont know if this function exists in MatrixSpace
p=W.coordinate_vector(V(lista(P[0])))
return p
```

Could you please provide the code of what you tried, so that we see where the problem is ?

@tmonteil done!

Could you please provide the constructon of the list of matrices ?