Python用上鎖和解鎖 lock lock.acquire lock.release 模擬搶火車票

Python用上鎖和解鎖  lock lock.acquire lock.release 模擬搶火車票

import json
import time
from multiprocessing import Process, Lock

# with open('catalogue.json', 'w') as fp:
# dic = {'total': 3}
# json.dump(dic, fp)


def check(buyers):
 with open('catalogue.json', mode='r') as fp:
 dic = json.load(fp)
 # print(dic,type(dict))
 print('%s 查詢余票：%s' % (buyers, dic['total']))


def buy_tickets(buyers):
 with open('catalogue.json', mode='r') as fp:
 dic = json.load(fp)
 time.sleep(0.8)
 if dic['total'] > 0:
 print('%s 買到票了' % buyers)
 dic['total'] -= 1
 with open('catalogue.json', 'w') as fp:
 json.dump(dic, fp)
 else:
 print('%s 沒買到這個票' % buyers)


def ticket_grabbing(buyers, lock):
 check(buyers)
 lock.acquire()
 buy_tickets(buyers)
 lock.release()


if __name__ == '__main__':
 lock = Lock()
 for i in range(10):
 p = Process(target=ticket_grabbing, args =('buyers%s' % i, lock))
 p.start()