python - How do I create a selection rectangle?

I have a basic prototype working with health, resources and units. The problem is: How do I select multiple units? I have an idea of making an rectangle which dynamically extends with the mouse position. I think I need to convert this rectangle to transparent rectangle.

Answer

pygame.draw.rect should be enough to draw transparent rectangles, according to documentation if you use width > 0, then the rectangle won't be filled.