Python colision detection

ColisionExample.py

class Rectangle:
	# defines x and y coords
	x = 0
	y = 0
	
	# defines width and height values. these must be positive
	w = 0
	h = 0
	
	def __init__(self, x, y, w, h):
		self.x = x
		self.y = y
		self.w = w
		self.h = h
	
	def validate(self):
		#checks that the rechangle has positive values
		if not(y <= (y + h) or x <= (x + w)):
			return False
		 # TODO more validation code
		else:
			return True
		 



# determines if 2 rectangles are colliding
def colides(rect1, rect2):
	# checks that both arguments are rectangles
	if not(isinstance(rect1, Rectangle) and isinstance(rect2, Rectangle)):
		raise ValueError("Must be instance of rectangle")
	
	# checks that both arguments are valid rectangles
	if not(rect1.validate() and rect2.validate()):
		raise ValueError("Rectangles Supplied are invalid")
	
	return (rect1.x > rect2.x) and (rect1.y > rect2.y) and ((rect2.x + rect2.w) > rect1.w) and ((rect2.y + rect2.h) > rect1.y)