Python NameError: name 'a' is not defined

if len(body):
    for (x,y,w,h) in body:
        cv2.rectangle(img1,(x,y),(x+w,y+h),(0,0,255),2)
        a = [(x+w),(y+h)]


if len(body):
    for (a,b,c,d) in body:
        cv2.rectangle(img2,(a,b),(a+c,b+d),(0,0,255),2)
        b = [(a+c),(b+d)]


if a[0] - b[0] <= [-5] or a[1] - b[1] >= [5]:
    print ("Out")
    break

  File "test3.py", line 49, in <module>
    if a[0] - b[0] <= [-5] or a[1] - b[1] >= [5]:
NameError: name 'a' is not defined