类方法@classmethod

def solve():
    class Date:
        def __init__(____):
            self.year = year
            self.month = month
            self.day = day
        @classmethod
        def from_string(____):
            y, m, d = s.split(____)
            return cls(int(____), int(____), int(____))
    d = Date.from_string(____)
    print(____)