How about this hit from googling "python minAreaRect":
https://www.programcreek.com/python/example/89463/cv2.minAreaRect
example 4 tells you:
# help(cv2.minAreaRect)
(x, y), (width, height), rect_angle = rectangle
so you could try that code. Or, if you just want to extract the fields from your rectangle, I guess rect[0] is (x, y) and rect[0][0] is x
and rect[1] is (width, height) and rect[1][0] is width
and so on, the other examples should help you.