A good question but also a very difficult one... According to the language that can vary a lot. Anyway, you have to:

• read the problem ;
• understand what you have to do ;
• think about the corner cases ;
• think how to do what you want ;
• implement your solution ;
• test and submit it;
• and most likely correct some things here and there.

And if you are not only new to Python, but also to programming in general, that can sure take a little time... That's a vague answer but I don't think you can reasonably expect a more precise one.