Yup,infact already did that. But I want to do it in python style :O:O
Python style is to make the best use of available tools--even if they aren't as efficient, they're more understandable. If you want a transparent image, you should just make a transparent image and go from there.
The only other way to this is to use colorkey transparency, which is somewhat harder and less obvious. Plus it restricts your color space, which can be annoying. Using a .png and calling .convert_alpha() as Eamonn said, is the best thing to do.
Ian