title: concatenate numpy arrays which are elements of a list
body: <p>I have a list containing numpy arrays something like L=[a,b,c] where a, b and c are numpy arrays with sizes N_a in T, N_b in T and N_c in T.<br>
  I want to row-wise concatenate a, b and c and get a numpy array with shape (N_a+N_b+N_c, T). Clearly one solution is run a for loop and use numpy.concatenate, but is there any pythonic way to do this?</p>
  
  <p>Thanks</p>