多线程复习 Rlock ,Condition,Semaphore
#对于io操作来说，多线程和多进程性能差别不大 #1.通过Thread类实例化 import time import threading def get_detail_html(url): print("get detail html started") time.sleep(2) print("get detail html end") def get_detail_url(url): print("get detail url started") time.sleep(4) print("get detail url end") #2. 通过集成Thread来实现多线程 class GetDetailHtml(threading.Thread): def __init__(self, name): super().__init__(name=name) def run(self): print("get detail html started") time.sleep(2) print("get detail html end") class GetDetailUrl(threading.Thread): def __init__(self, name): super().__init__(name=name) def run(self): print("get detail url started") time.sleep(4) print("get detail url end") if __name__ == "__main__": thread1 = GetDetailHtml("get_detail_html") thread2 = GetDetailUrl("get_detail_url") start_time = time.time() thread1.start() thread2.start() thread1.join() thread2.join() #当主线程退出的时候， 子线程kill掉 print ("last time: {}".format(time.time()-start_time))
线程间通信 -Queue
#通过queue的方式进行线程间同步 from queue import Queue import time import threading def get_detail_html(queue): #爬取文章详情页 while True: url = queue.get() # for url in detail_url_list: print("get detail html started") time.sleep(2) print("get detail html end") def get_detail_url(queue): # 爬取文章列表页 while True: print("get detail url started") time.sleep(4) for i in range(20): queue.put("http://projectsedu.com/{id}".format(id=i)) print("get detail url end") #1. 线程通信方式- 共享变量 if __name__ == "__main__": detail_url_queue = Queue(maxsize=1000) thread_detail_url = threading.Thread(target=get_detail_url, args=(detail_url_queue,)) for i in range(10): html_thread = threading.Thread(target=get_detail_html, args=(detail_url_queue,)) html_thread.start() # # thread2 = GetDetailUrl("get_detail_url") start_time = time.time() # thread_detail_url.start() # thread_detail_url1.start() # # thread1.join() # thread2.join() detail_url_queue.task_done() detail_url_queue.join() #当主线程退出的时候， 子线程kill掉 print ("last time: {}".format(time.time()-start_time))
线程锁，lock和Rlock
from threading import Lock, RLock, Condition #可重入的锁 #在同一个线程里面，可以连续调用多次acquire， 一定要注意acquire的次数要和release的次数相等 total = 0 lock = RLock() def add(): #1. dosomething1 #2. io操作 # 1. dosomething3 global lock global total for i in range(1000000): lock.acquire() lock.acquire() total += 1 lock.release() lock.release() def desc(): global total global lock for i in range(1000000): lock.acquire() total -= 1 lock.release() import threading thread1 = threading.Thread(target=add) thread2 = threading.Thread(target=desc) thread1.start() thread2.start() # thread1.join() thread2.join() print(total) #1. 用锁会影响性能 #2. 锁会引起死锁 #死锁的情况 A（a，b） """ A(a、b) acquire (a) acquire (b) B(a、b) acquire (a) acquire (b) """
条件变量-线程间同步
import threading #条件变量， 用于复杂的线程间同步 # class XiaoAi(threading.Thread): # def __init__(self, lock): # super().__init__(name="小爱") # self.lock = lock # # def run(self): # self.lock.acquire() # print("{} : 在 ".format(self.name)) # self.lock.release() # # self.lock.acquire() # print("{} : 好啊 ".format(self.name)) # self.lock.release() # # class TianMao(threading.Thread): # def __init__(self, lock): # super().__init__(name="天猫精灵") # self.lock = lock # # def run(self): # # self.lock.acquire() # print("{} : 小爱同学 ".format(self.name)) # self.lock.release() # # self.lock.acquire() # print("{} : 我们来对古诗吧 ".format(self.name)) # self.lock.release() #通过condition完成协同读诗 class XiaoAi(threading.Thread): def __init__(self, cond): super().__init__(name="小爱") self.cond = cond def run(self): with self.cond: self.cond.wait() print("{} : 在 ".format(self.name)) self.cond.notify() self.cond.wait() print("{} : 好啊 ".format(self.name)) self.cond.notify() self.cond.wait() print("{} : 君住长江尾 ".format(self.name)) self.cond.notify() self.cond.wait() print("{} : 共饮长江水 ".format(self.name)) self.cond.notify() self.cond.wait() print("{} : 此恨何时已 ".format(self.name)) self.cond.notify() self.cond.wait() print("{} : 定不负相思意 ".format(self.name)) self.cond.notify() class TianMao(threading.Thread): def __init__(self, cond): super().__init__(name="天猫精灵") self.cond = cond def run(self): with self.cond: print("{} : 小爱同学 ".format(self.name)) self.cond.notify() self.cond.wait() print("{} : 我们来对古诗吧 ".format(self.name)) self.cond.notify() self.cond.wait() print("{} : 我住长江头 ".format(self.name)) self.cond.notify() self.cond.wait() print("{} : 日日思君不见君 ".format(self.name)) self.cond.notify() self.cond.wait() print("{} : 此水几时休 ".format(self.name)) self.cond.notify() self.cond.wait() print("{} : 只愿君心似我心 ".format(self.name)) self.cond.notify() self.cond.wait() if __name__ == "__main__": from concurrent import futures cond = threading.Condition() xiaoai = XiaoAi(cond) tianmao = TianMao(cond) #启动顺序很重要 #在调用with cond之后才能调用wait或者notify方法 #condition有两层锁， 一把底层锁会在线程调用了wait方法的时候释放， 上面的锁会在每次调用wait的时候分配一把并放入到cond的等待队列中，等到notify方法的唤醒 xiaoai.start() tianmao.start()
Semaphore 是用于控制进入数量的锁
#Semaphore 是用于控制进入数量的锁 #文件， 读、写， 写一般只是用于一个线程写，读可以允许有多个 #做爬虫 import threading import time class HtmlSpider(threading.Thread): def __init__(self, url, sem): super().__init__() self.url = url self.sem = sem def run(self): time.sleep(2) print("got html text success") self.sem.release() class UrlProducer(threading.Thread): def __init__(self, sem): super().__init__() self.sem = sem def run(self): for i in range(20): self.sem.acquire() html_thread = HtmlSpider("https://baidu.com/{}".format(i), self.sem) html_thread.start() if __name__ == "__main__": sem = threading.Semaphore(3) url_producer = UrlProducer(sem) url_producer.start()
