i know using datetime.timedelta i can get the date of some days away form given date
daysafter = datetime.date.today() + datetime.timedelta(days=5)
You can use calendar.nextmonth
(from Python 3.7).
>>> import calendar
>>> calendar.nextmonth(year=2019, month=6)
(2019, 7)
>>> calendar.nextmonth(year=2019, month=12)
(2020, 1)
But be aware that this function isn't meant to be public API, it's used internally in calendar.Calendar.itermonthdays3() method. That's why it doesn't check the given month value:
>>> calendar.nextmonth(year=2019, month=60)
(2019, 61)
In Python 3.8 is already implemented as internal function.