Arranging numpy arrays in a block matrix

Question

I have 3 numpy arrays A, B and C. For simplicity, let\'s assume that they are all of shape [n, n]. I want to arrange them as

Answer 1

Stripped of some bells and whisles, np.bmat does this:

def foo(alist):
    rowlist=[]
    for row in alist:
        rowlist.append(np.concatenate(row,axis=1))
    return np.concatenate(rowlist, axis=0)

So for example:

In [1026]: A=np.arange(4).reshape(2,2);B=np.arange(2).reshape(2,1);C=np.array([0]).reshape(1,1)

In [1027]: foo([[A,B],[B.T,C]])
Out[1027]: 
array([[0, 1, 0],
       [2, 3, 1],
       [0, 1, 0]])

Making the inputs matrices simplifies the reshape preparation.