[Python3] One line solution.
Code\n\nclass Solution:\n    def successfulPairs(self, spells: List[int], potions: List[int], success: int) -> List[int]:\n        return potions.sort() or [len
# Code\n```\nclass Solution:\n    def successfulPairs(self, spells: List[int], potions: List[int], success: int) -> List[int]:\n        return potions.sort() or [len(potions) - bisect_left(potions, -(-success // spell)) for spell in spells]\n\n```
['Python3']