Maybe these examples will help you get an idea:
from dateutil.relativedelta import relativedelta
import datetime
date1 = datetime.datetime.strptime("2015-01-30", "%Y-%m-%d").strftime("%d-%m-%Y")
print(date1)
today = datetime.date.today()
print(today)
addMonths = relativedelta(months=3)
future = today + addMonths
print(future)
If you import datetime it will give you more options in managing date and time variables.
In my example above I have some example code that will show you how it works.
It is also very usefull if you would for example would like to add a x number of days, months or years to a certain date.
Edit:
To answer you question below this post I would suggest you to look at "calendar"
For example:
import calendar
january2012 = calendar.monthrange(2002,1)
print(january2012)
february2008 = calendar.monthrange(2008,2)
print(february2008)
This return you the first workday of the month, and the number of days of the month.
With that you can calculate what was the last workday of the month.
Here is more information about it: Link
Also have a loook here, looks what you might could use: Link