MyDate

ddleap = [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
ddnleap = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]


class MyDate:

    def __init__(self, dd, mm, yy):
        self.day = dd
        self.month = mm
        self.year = yy

        def setleap(year):
            '''calcola la bisestilità dell'anno'''
            if not (year % 400) or (not (year % 4) and year % 100):
                self.leap = True
            else:
                self.leap = False

        setleap(yy)
        if self.leap:
            self.mmdays = ddleap
        else:
            self.mmdays = ddnleap

        def setesimo(leap):
            '''calcola il numero ordinale del giorno nell'anno inserito tenendo conto della bisestilitò'''
            ddth = 0
            for index, ai in enumerate(self.mmdays):
                if index >= self.month - 1:
                    ddth += self.day
                    break
                else:
                    ddth += ai

            self.ordinale = ddth

        setesimo(self.leap)

    def sumdate(self, num):
        '''calcola la nuova data sommando il num'''
        month = self.month - 1
        year = self.year
        mmdays = self.mmdays
        def myupdate(month, year):
            month += 1
            if not month % 12:
                month = 0
                year += 1

        distance = mmdays[month] - self.day
        if num <= distance:
            return str(str(self.day + num) + "/" + str(month + 1) + "/" + str(year))

        num -= distance
        month += 1
        if not month % 12:
            month = 0
            year += 1

        while num > mmdays[month]:
            if not (year % 400) or (not (year % 4) and year % 100):
                leap = True
            else:
                leap = False
            if leap:
                mmdays = ddleap
            else:
                mmdays = ddnleap
            num -= mmdays[month]
            month += 1
            if not month % 12:
                month = 0
                year += 1

        return str(str(num) + "/" + str(month + 1) + "/" + str(year))


a = MyDate(5, 8, 2021)

if __name__ == '__main__':
    print(a.day, a.month, a.year, "\n" + a.sumdate(5000))