python instance methods, static methods, class methods

class Date:
    #构造函数
    def __init__(self, year, month, day):
        self.year = year
        self.month = month
        self.day = day

    def tomorrow(self):
        self.day += 1

    @staticmethod
    def parse_from_string(date_str):
        year, month, day = tuple(date_str.split("-"))
        return Date(int(year), int(month), int(day))

    @staticmethod
    def valid_str(date_str):
        year, month, day Tuple = (date_str.split ( " - " ))
         IF int (year)> 0 and (int (month The)> 0 and int (month The) <= 12 is) and (int (Day)> 0 and int (Day) < 31 = ):
             return True
         the else :
             return False 

    @classmethod 
    DEF from_string (CLS, DATE_STR): 
        year, month The, Day = tuple (date_str.split ( " - " ))
         return CLS (int (year), int (month The), int (day)) # here If the class name has changed, then, when we return to class instance, would not return to the class name of the

     DEF  __str__(self):
        return "{year}/{month}/{day}".format(year=self.year, month=self.month, day=self.day)

if __name__ == "__main__":
    new_day = Date(2018, 12, 31)
    new_day.tomorrow()
    print(new_day)

    #2018-12-31
    date_str = "2018-12-31"
    year, month, day = tuple(date_str.split("-"))
    new_day = Date(int(year), int(month), int(day))
    print (new_day)

    #Initialization is completed with staticmethod 
    new_day = Date.parse_from_string (DATE_STR)
     Print (new_day) 

    # with classmethod complete initialization 
    new_day = Date.from_string (DATE_STR)
     Print (new_day) 

    Print (Date.valid_str ( " 2018-12-32 " ))