import threading
g_num = 0
def test(n):
    global g_num
    for x in range(n):
        g_num += x
        g_num -= x
    print(g_num)
if __name__ == '__main__':
    t1 = threading.Thread(target=test, args=(10,))
    t2 = threading.Thread(target=test, args=(10,))
    t1.start()
    t2.start()

import threading
import time
ticket = 20
def sell_ticket():
    global ticket
    while True:
        if ticket > 0:
            time.sleep(0.5)
            ticket -= 1
            print('{}卖了一张票，还剩{}'.format(threading.current_thread().name, ticket))
        else:
            print('{}票卖完了'.format(threading.current_thread().name))
            break
for i in range(5):
    t = threading.Thread(target=sell_ticket, name='thread-{}'.format(i + 1))
    t.start()