adding numbers in two lists

#a = [9,9,9]
#b = [1,1]
#[1, 0, 2, 0]
def sol(a,b):
    a,b = a[::-1], b[::-1]
    if len(b)>len(a):
        a,b = b,a
    b.extend([0]*(len(a)-len(b)))
    res = [0]*len(a)
    for i in range(len(a)-1):
        temp=res[i]+a[i]+b[i]
        res[i]+=temp%10
        res[i+1]=temp//10
    temp = res[-1]+ a[-1]+b[-1]
    res[-1] = temp%10
    if temp>9:
        res.append(temp//10)
    return res[::-1]