python多线程调用规范

import threading
import time
import random


# threading.Thread(target=None, args=())
def hello():
    time.sleep(random.random())
    print("hello world  %d" % threading.active_count())
arr = []
def wait():
    for x in arr:
        x.join()
    print("所有程序执行完毕")
# hello()

for x in range(10):
    t = threading.Thread(target=hello)
    t.start()
    arr.append(t)


threading.Thread(target=wait).start()
print("没有阻塞")
# 没有阻塞