Add to Array-Form of Integer

class Solution:
    def addToArrayForm(self, num, k):
        k = list(map(int, list(str(k))))
        c = 0
        res = []
        while k or num:
            s = c + (0 if not k else k.pop()) + (0 if not num else num.pop())
            c = s // 10
            s = s % 10
            res.append(s)
        if c: res.append(c)
        return res[::-1]