#python threading
import time
'''
  每一秒中，输出：this is a demo!
'''
def serial():
  '''串行输出'''
  time.sleep(1)
  print('this is a demo!')
def main():
  for i in range(5):
    serial()
if __name__ == '__main__':
  main()

>>> 
this is a demo!
this is a demo!
this is a demo!
this is a demo!
this is a demo!
>>>

#python threading
import threading
import time
'''
  并行执行，输出：Good!Good!Good!Good!Good!
'''
def parallel():
  '''并行输出'''
  time.sleep(1)
  print('Good!')
def main():
  for i in range(5):
    t = threading.Thread(target=parallel)
    t.start()
if __name__ == '__main__':
  main()

#python threading
import threading
import time
'''
  并行执行，输出：
  [<Thread(Thread-2, started 3480)>, <Thread(Thread-1, started 660)>,
  <Thread(SockThread, started daemon 2920)>, <Thread(Thread-3, started 916)>,
  <Thread(Thread-4, started 3476)>, <_MainThread(MainThread, started 3964)>,
  <Thread(Thread-5, started 2060)>]
  存在的线程数 ： 7
  Good!Good!Good!Good!Good!
'''
def parallel():
  '''并行输出'''
  time.sleep(1)
  print('Good!')
def main():
  for i in range(5):
    t = threading.Thread(target=parallel)
    t.start()
if __name__ == '__main__':
  main()
  print(threading.enumerate())
  print('存在的线程数 ： %d'%threading.active_count())

>>> 
[<Thread(SockThread, started daemon 15424)>, <Thread(Thread-3, started 15840)>, <Thread(Thread-1, started 10884)>, <Thread(Thread-2, started 14512)>, <Thread(Thread-4, started 13204)>, <_MainThread(MainThread, started 12924)>, <Thread(Thread-5, started 15476)>]
存在的线程数 ： 7
>>> Good!Good!Good!Good!Good!