How do you write a Python program that takes DNA sequence and give number of ORFs found in the sequence?
One thing you should be careful of when posting in this forum is that not everyone knows the context of your problem. Python is a multi-dimensional language which can be used to do anything from writing letters to solving partial differential equations. As such, when posting, you need to to outline a proper context for your problem and show some effort to have solved it. I don't think most people on this forum are likely to be biologists with the same background as you, so you should do the following:
Post a sample of your data, in this case DNA sequence data.
Explain what it is you are trying to do. In this case, I think many people on this forum will easily understand what an open reading frame is without the biological context.
Third, and probably key, is to demonstrate that you have put in some effort on your own to solve the problem, so that you don't give off the vibe that you want someone else to do the work for you.
You may also consider looking into the BioPython addon, which is a free package for Bio analysis which may already have this feature built in. If not, then post more information here and we can help.