[python] zip split, generator sum 5-liner (or 3 lines minified) - beats 100%
```\nfrom itertools import chain\n\n\nclass Solution:\n    def digitSum(self, s: str, k: int) -> str:\n        string = s\n        tail = \'0\' * (k - 1)\n     
```\nfrom itertools import chain\n\n\nclass Solution:\n    def digitSum(self, s: str, k: int) -> str:\n        string = s\n        tail = \'0\' * (k - 1)\n        while len(string) > k:\n            parts = list(\n                zip(\n                    *(\n                        [iter(\n                            chain(string, tail)\n                        )] * k\n                    )\n                )\n            )\n            string = \'\'.join(\n                str(\n                    sum(\n                        int(number) for number in part\n                    )\n                ) for part in parts\n            )\n        return string\n\t\t\n\t\t# ...or packed into (almost) one-liner\n\t\t#while len(s) > k:\n        #    s = \'\'.join(str(sum(int(number) for number in part)) for part in zip(*([iter(chain(s, \'0\' * (k - 1)))] * k)))\n        #return s
['String', 'Iterator', 'Python']