How to write a timestamp and number of detections to the log in basic-motion-detection?

Question

CCTV

Downloaded from here
https://www.pyimagesearch.com/2015/05/25/basic-mot...
file motion_detector.py, with content:

spoiler

# USAGE
# python motion_detector.py
# python motion_detector.py --video videos/example_01.mp4

# import the necessary packages
from imutils.video import VideoStream
import argparse
import datetime
import imutils
import time
import cv2

# construct the argument parser and parse the arguments
ap = argparse.ArgumentParser()
ap.add_argument("-v", "--video", help="path to the video file")
ap.add_argument("-a", "--min-area", type=int, default=500, help="minimum area size")
args = vars(ap.parse_args())

# if the video argument is None, then we are reading from webcam
if args.get("video", None) is None:
  vs = VideoStream(src=0).start()
  time.sleep(2.0)

# otherwise, we are reading from a video file
else:
  vs = cv2.VideoCapture(args["video"])

# initialize the first frame in the video stream
firstFrame = None

# loop over the frames of the video
while True:
  # grab the current frame and initialize the occupied/unoccupied
  # text
  frame = vs.read()
  frame = frame if args.get("video", None) is None else frame[1]
  text = "Unoccupied"

  # if the frame could not be grabbed, then we have reached the end
  # of the video
  if frame is None:
    break

  # resize the frame, convert it to grayscale, and blur it
  frame = imutils.resize(frame, width=500)
  gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
  gray = cv2.GaussianBlur(gray, (21, 21), 0)

  # if the first frame is None, initialize it
  if firstFrame is None:
    firstFrame = gray
    continue

  # compute the absolute difference between the current frame and
  # first frame
  frameDelta = cv2.absdiff(firstFrame, gray)
  thresh = cv2.threshold(frameDelta, 25, 255, cv2.THRESH_BINARY)[1]

  # dilate the thresholded image to fill in holes, then find contours
  # on thresholded image
  thresh = cv2.dilate(thresh, None, iterations=2)
  cnts = cv2.findContours(thresh.copy(), cv2.RETR_EXTERNAL,
    cv2.CHAIN_APPROX_SIMPLE)
  cnts = imutils.grab_contours(cnts)

  # loop over the contours
  for c in cnts:
    # if the contour is too small, ignore it
    if cv2.contourArea(c) < args["min_area"]:
      continue

    # compute the bounding box for the contour, draw it on the frame,
    # and update the text
    (x, y, w, h) = cv2.boundingRect(c)
    cv2.rectangle(frame, (x, y), (x + w, y + h), (0, 255, 0), 2)
    text = "Occupied"

  # draw the text and timestamp on the frame
  cv2.putText(frame, "Room Status: {}".format(text), (10, 20),
    cv2.FONT_HERSHEY_SIMPLEX, 0.5, (0, 0, 255), 2)
  cv2.putText(frame, datetime.datetime.now().strftime("%A %d %B %Y %I:%M:%S%p"),
    (10, frame.shape[0] - 10), cv2.FONT_HERSHEY_SIMPLEX, 0.35, (0, 0, 255), 1)

  # show the frame and record if the user presses a key
  cv2.imshow("Security Feed", frame)
  cv2.imshow("Thresh", thresh)
  cv2.imshow("Frame Delta", frameDelta)
  key = cv2.waitKey(1) & 0xFF

  # if the `q` key is pressed, break from the lop
  if key == ord("q"):
    break

# cleanup the camera and close any open windows
vs.stop() if args.get("video", None) is None else vs.release()
cv2.destroyAllWindows()

and even some sort of instruction
https://www.pyimagesearch.com/static/cv_dl_resourc...

The file was even launched on ubuntu 16.04
You can specify a video file - and it will look for movements in it,
you can not specify it - then it will take webcam stream.

The question is this: hint in which line you can modify the code to write lines like:
"timestamp: number of detections" in log.txt
?