Say I have two matrices
B
M
B += 3*M
3*M
3
as
Ms
sum(a*M for a, M in zip(as, Ms))
np.dot
You can use np.tensordot

np.tensordot(As,Ms,axes=(0,0))
Or np.einsum

np.einsum('i,ijk>jk',As,Ms)
Sample run 
In [41]: As = [2,5,6]
In [42]: Ms = [np.random.rand(2,3),np.random.rand(2,3),np.random.rand(2,3)]
In [43]: sum(a*M for a, M in zip(As, Ms))
Out[43]:
array([[ 6.79630284, 5.04212877, 10.76217631],
[ 4.91927651, 1.98115548, 6.13705742]])
In [44]: np.tensordot(As,Ms,axes=(0,0))
Out[44]:
array([[ 6.79630284, 5.04212877, 10.76217631],
[ 4.91927651, 1.98115548, 6.13705742]])
In [45]: np.einsum('i,ijk>jk',As,Ms)
Out[45]:
array([[ 6.79630284, 5.04212877, 10.76217631],
[ 4.91927651, 1.98115548, 6.13705742]])