I've just started working with pygame and I'm trying to make a semi-transparent sprite, and the sprite's source file is a non-transparent bitmap file loaded from the disk. I don't want to edit the source image if I can help it. I'm sure there's a way to do this with pygame code, but Google is of no help to me.
you might consider switching to using png images where you can do any kind of transparency you want directly in the image.
How to make translucent sprites in pygame