Dumber but working

a = [[2,3,4],
    [5,6,7],
    [8,9,10],
    [11,12,13],
    [14,15,16]]










def average(a,w,h):
    c=[]
    for y in range(0,h):
        l=[]
        m=[]
        r=[]
        for i in range(y-1,y+2):
                if i>=0 and i<h:
                    m.append(a[i][0])
                    r.append(a[i][1])
        R=[]
        for x in range(1,w+1):
            R.append((int)((sum(l)+sum(m)+sum(r))/(len(l)+len(m)+len(r))))
            l=m
            m=r
            r=[]
            for i in range(y-1,y+2):
                if i>=0 and i<h and x+1<w:
                    r.append(a[i][x+1])
        c.append(R)
    return c











avr = average(a, 3, 5)

print ("a: ")
for R in a:
    print (R)


print ("\n\n\naverage: ")
for R in avr:
    print (R)