import threading
import time
 
sem=threading.Semaphore(4) #限制线程的最大数量为4个
 
def gothread():
  with sem: #锁定线程的最大数量
    for i in range(8):
      print(threading.current_thread().name,i)
      time.sleep(1)
 
for i in range(5):
  threading.Thread(target=gothread).start()