Найти произведение матриц

def dot_prod( L, R ):
    res = 0
    for i in range( len(L) ):
        res += L[i]*R[i]
    return res
#==============================================================================
n_A, m_A = list( map( int, input('n_A, m_A = ').split() )  )
A = []
for i in range(n_A):
    A.append( list( map( int, input('-> ').split() ) ) )
print()
m_B, k_B = list( map( int, input('m_B, k_B = ').split() ) )
B = []
for i in range(m_B):
    B.append( list( map( int, input('-> ').split() ) ) )
B_tr = []
for col in zip(*B):
    B_tr.append(col)
C = [[dot_prod( A[i], B_tr[k] ) for k in range(k_B)] for i in range(n_A) ]
print()
for e in C:
    print(*e)

def mult_matr(a,b):
    ca=len(a[0])
    rb=len(b)
    if ca != rb:
        return None
    res=[]
    for r in range(len(a)):
        rr=[]
        for c in range(len(b[0])):
             s=0
             for k in range(ca):
                 s=s+a[r][k]*b[k][c]
             rr.append(s)
        res.append(rr)
    return res
   
   
(r,c)=map(int,input().split())
aa=[]
for _ in range(r):
    row=list(map(int,input().split()))
    aa.append(row)
    
(r,c)=map(int,input().split())
bb=[]
for _ in range(r):
    row=list(map(int,input().split()))
    bb.append(row)    
    
print(mult_matr(aa,bb))

n_A, m_A = list( map( int, input('n_A, m_A = ').split() )  )
A = []
for i in range(n_A):
    A.append( list( map( int, input('-> ').split() ) ) )
print()
m_B, k_B = list( map( int, input('m_B, k_B = ').split() ) )
B = []
for i in range(m_B):
    B.append( list( map( int, input('-> ').split() ) ) )
B_tr = []
for col in zip(*B):
    B_tr.append(col)
C = [ [sum( [ A[i][j] * B_tr[k][j] for j in range( len(A[i] ) ) ] ) for k in range(k_B) ] for i in range(n_A) ]
print()
for e in C:
    print(*e)