You must program on your level raising it little by little. Can you give example of easy program you finished until working condition and hardest program you did until now? Have you not been able to finish any program? Have you done some programs suggested in sticky threads in begining of Python forum threads?
While I don't quite understand the language in that program, I do understand what your program is doing. So it looks like you've just started using classes. How about creating a program utilizing a GUI, I suggest tkinter for its simplicity.
First,learn how to implement the basics you're learning into something useful, while you are doing that you may find that you want to add more features, those features may require you to learn more advanced things. For example, recently I learned how to utilize SMTP to send E-mails from a program. As you do this you will learn more advanced skills and gain knowledge of third-party modules as well as built-in modules you haven't yet had to use.
#please do not use old style classes in new programs
# pass does not make sense in class definition if you have defined something
# function not using instance variables (__slot__ or __init__ initialized)
# what is the benefit of the class here
# so you are using Python2 (raw_input, print not function)
# a does not mean anything to me, add prompt does not make clear that we should input integer value
if (a<= 15):
# why not else as this is all other numbers?
a = Abc()