python のファイル全体の実行時間の計測方法

import pytz
from datetime import datetime

def main():
    print("Hello world!")

if __name__ == "__main__":

    start = datetime.now(pytz.timezone('Asia/Tokyo'))
    print()
    main()
    print()


    print("Train Started at {}".format(start))
    finish = datetime.now(pytz.timezone('Asia/Tokyo'))
    print("Train Finished at {}".format(finish))
    print("Elapsed Time: {}".format(finish - start))