只需将所有内容 Package 在while True:中，如下所示：

import cv2
import time
from datetime import datetime
import schedule
import os
import sys
import numpy as np
from os import path

while True:
    cap = cv2.VideoCapture(0)
    if (cap.isOpened() == False):
       print("Error reading video file")
    fps = 24
    res = '480p'
    def change_res(cap, width, height):
       cap.set(3, width)
       cap.set(4, height)
    STD_DIMENSIONS =  {"480p": (640, 480),"720p": (1280, 720),}
    def get_dims(cap, res='720p'):
       width, height = STD_DIMENSIONS["480p"]
       if res in STD_DIMENSIONS:
           width,height = STD_DIMENSIONS[res]
       change_res(cap, width, height)
       return width, height
    PREFIX = 'Cam'
    EXTENSION = 'avi'
    file_name_format = "{:s}-{:%d-%m-%Y %H:%M-%S}.{:s}"
    date = datetime.now()
    today=time.strftime('%d-%m-%Y')
    file_name = file_name_format.format(PREFIX, date, EXTENSION)
    fourcc = cv2.VideoWriter_fourcc(*'XVID')
    out = cv2.VideoWriter (file_name, fourcc, 24.0, get_dims(cap, res))

    start_time = time.time()
    while (time.time() - start_time) < 5:
       ret, frame = cap.read()
       if ret == True:
           out.write(frame)
           cv2.imshow('CAM', frame)
       if cv2.waitKey(1) & 0xFF == ord('q'):
          break

    cap.release()
    out.release()
    cv2.destroyAllWindows()

或者你可以在循环中添加一个计数器来代替while True:，例如当计数器达到某个值时跳出循环。