You mean “python and ObjctiveC” and not “Swift”.
How to draw stuff
This is the documentation from Apple: Introduction to Cocoa Drawing Guide
rect = NSMakeRect(10, 10, 20, 20)
NSColor.colorWithRed_green_blue_alpha_(0.2, 0.8, 0.4, 1).set()
path = NSBezierPath.bezierPathWithRect_(rect)
path.fill()