Tracking Moving Object - Python(OpenCV)

import numpy as np
import cv2 as cv
cap = cv.VideoCapture('traffic.mp4')
#take first frame of the video
ret, frame = cap.read()
#setup initial location of window
x, y, width, height = 250, 2, 100, 50
track_window = (x, y, width, height)
#set up the ROI for tracking
roi = frame[y : y+height, x : x+width]
hsv_roi = cv.cvtColor(roi, cv.COLOR_BGR2HSV)
mask = cv.inRange(hsv_roi, np.array((0., 60., 32.)), np.array((180., 255., 255)))
roi_hist = cv.calcHist([hsv_roi], [0], mask, [180], [0, 180])
cv.normalize(roi_hist, roi_hist, 0, 255, cv.NORM_MINMAX)
#set the termination criteria, either 10 iteration or move by atleast 1 pt
term_crit = (cv.TERM_CRITERIA_EPS | cv.TERM_CRITERIA_COUNT, 10, 1)

cv.imshow('roi', roi)
while(1):
    ret, frame = cap.read()
    if ret == True:
        hsv = cv.cvtColor(frame, cv.COLOR_BGR2HSV)
        dst = cv.calcBackProject([hsv], [0], roi_hist, [0, 180], 1)
        #apply meanshift to get the new location
       # ret, track_window = cv.meanShift(dst, track_window, term_crit)

        #change marked rectangle according its target
        ret, track_window = cv.CamShift(dst, track_window, term_crit)
        #print(ret)
        pts = cv.boxPoints(ret)
        #print(pts)
        pts = np.int0(pts)
        final_image = cv.polylines(frame, [pts], True, (0, 255, 0), 2)
        #Draw it on image
        #x, y, w, h = track_window
        #final_image = cv.rectangle(frame, (x,y), (x+w, y+h), 255, 3)

        cv.imshow('dst', dst)
        cv.imshow('final_image', final_image)
        k=cv.waitKey(30) & 0xff
        if k == 27:
            break
    else:
        break