gj11 多线程、多进程和线程池编程

11.1 python中的GIL

# coding=utf-8
# gil global interpreter lock （cpython）
# python中一个线程对应于c语言中的一个线程
# gil使得同一个时刻只有一个线程在一个cpu上执行字节码, 无法将多个线程映射到多个cpu上执行

# gil会根据执行的字节码行数以及时间片释放gil，
# gil在遇到io的操作时候主动释放

import dis

def add(a):
    a = a + 1
    return a

print(dis.dis(add))
total = 0

def add():
    # 1. dosomething1
    # 2. io操作
    # 1. dosomething3
    global total
    for i in range(1000000):
        total += 1

def desc():
    global total
    for i in range(1000000):
        total -= 1

import threading

thread1 = threading.Thread(target=add)
thread2 = threading.Thread(target=desc)
thread1.start()
thread2.start()

thread1.join()
thread2.join()
print(total)

# 在IO频繁的时候是很适合的

执行多少行后字节码会释放

11.2 python多线程编程

操作系统最小的执行单元

# coding=utf-8
# __auther__ = 'lewen'

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")

if __name__ == "__main__":
    # 在主线程起两个线程
    thread1 = threading.Thread(target=get_detail_html, args=("",))
    thread2 = threading.Thread(target=get_detail_url, args=("",))
    #     thread1.setDaemon(True)
    # thread2.setDaemon(True)  # 守护线程，当主线程退出的时候， 子线程kill掉

    start_time = time.time()
    thread1.start()
    thread2.start()

    thread1.join()  # 等待线程的执行完成，才会执行下面
    thread2.join()

    print("last time: {}".format(time.time() - start_time))

通过集成Thread来实现多线程

class GetDetailHtml(threading.Thread):
    def __init__(self, name):
        # py2 必须在括号写类名
        # 继承父类的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()

    print("last time: {}".format(time.time() - start_time))

11.3 线程间通信-Queue

共用变量

# 线程间通信

import time
import threading
from chapter11 import variables

from threading import Condition

detail_url_list = []

# 1. 生产者当生产10个url以后就就等待，保证detail_url_list中最多只有十个url
# 2. 当url_list为空的时候，消费者就暂停

def get_detail_html(lock):
    # 爬取文章详情页
    detail_url_list = variables.detail_url_list  # 将共享变量存放到文件中去
    while True:

        if len(variables.detail_url_list):
               if len(detail_url_list):
                url = detail_url_list.pop()
                # for url in detail_url_list:
                print("get detail html started")
                time.sleep(2)
                print("get detail html end")
            else:
                time.sleep(1)

def get_detail_url(lock):
    # 爬取文章列表页
    detail_url_list = variables.detail_url_list
    while True:
        print("get detail url started")
        time.sleep(4)
        for i in range(20):
            if len(detail_url_list) >= 10:
                time.sleep(1)
            else:
                detail_url_list.append("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__":
    thread_detail_url = threading.Thread(target=get_detail_url, args=(lock,))
    for i in range(10):
        html_thread = threading.Thread(target=get_detail_html, args=(lock,))
        html_thread.start()
    # # thread2 = GetDetailUrl("get_detail_url")
    start_time = time.time()

    # 当主线程退出的时候， 子线程kill掉
    print("last time: {}".format(time.time() - start_time))

# 通过共用变量

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()  # 阻塞，没有会停在这
        print(url)
        # 内部基于deque
        print("get detail html started")
        time.sleep(1)
        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(2)
        for i in range(9):
            queue.put("http://www.baidu.com/s?wd=".format(id=i))
        print(queue.qsize())
        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,))

    html_thread_list = []
    for i in range(10):
        html_thread = threading.Thread(target=get_detail_html, args=(detail_url_queue,))
        html_thread.start()
        html_thread_list.append(html_thread)
    start_time = time.time()

    for h in html_thread_list:
        h.join()
    # detail_url_queue.join()  # 这里想退出，必须等到 detail_url_queue.task_done()调用，才会退出

    print("last time: {}".format(time.time() - start_time))

# 通过queue的方式进行线程间同步

11.4 线程同步（Lock、RLock、Semaphores、Condition）

from threading import Lock, RLock, Condition  # 可重入的锁

# Lock 不能重复调用
total = 0
lock = RLock()  # 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
                # 多个线程之间仍会竞争

def add():

    global lock
    global total
    for i in range(1000000):
        lock.acquire()
        lock.acquire()   # 一个线程里面重入的锁
        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)   # 阻塞住，死在这

B(b、a)
acquire (b)   # 交互死锁，资源竞争
acquire (a)
"""

Lock、RLock

condition 使用以及源码分析

import threading

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()
if __name__ == "__main__":

    lock = threading.Lock()

    xiaoai = XiaoAi(lock)
    tianmao = TianMao(lock)

    tianmao.start()
    xiaoai.start()

# ---
天猫精灵 : 小爱同学
天猫精灵 : 我们来对古诗吧
小爱 : 在
小爱 : 好啊

没有使用condition

class XiaoAi(threading.Thread):
    def __init__(self, cond):
        super().__init__(name="小爱")
        self.cond = cond

    def run(self):
        with self.cond:#第一把锁
            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:  #第一把锁
            print("{} : 小爱同学 ".format(self.name))
            self.cond.notify()  # 提醒
            self.cond.wait()    # 等待条件提醒

            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__":

    cond = threading.Condition()
    xiaoai = XiaoAi(cond)
    tianmao = TianMao(cond)

    # 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(with condition)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()

    # 启动顺序很重要
    # 天猫start 后 notify ，然后小爱 start 进入wait ，一直接受不到 notify 就阻塞住
    # start 后 wait 的线程应该先启动去等着，以免接受不到notify

# ---
天猫精灵 : 小爱同学
小爱 : 在
天猫精灵 : 我们来对古诗吧
小爱 : 好啊
天猫精灵 : 我住长江头
小爱 : 君住长江尾
天猫精灵 : 日日思君不见君
小爱 : 共饮长江水
天猫精灵 : 此水几时休
小爱 : 此恨何时已
天猫精灵 : 只愿君心似我心
小爱 : 定不负相思意

 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(with condition)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

Semaphore 使用

# 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()

11.5 concurrent线程池编码

# 线程池， 为什么要线程池
# 主线程中可以获取某一个线程的状态或者某一个任务的状态，以及返回值
# 当一个线程完成的时候我们主线程能立即知道
# futures可以让多线程和多进程编码接口一致

from concurrent.futures import ThreadPoolExecutor, as_completed, wait, FIRST_COMPLETED
import time

def get_html(times):
    time.sleep(times)
    print("get page {} success".format(times))
    return times
executor = ThreadPoolExecutor(max_workers=2)

# 通过submit函数提交执行的函数到线程池中, submit 是立即返回
task1 = executor.submit(get_html, (3))
task2 = executor.submit(get_html, (2))

# done方法用于判定某个任务是否完成
print(task1.done())

# print(task2.cancel())   # 取消任务(成功返回True)，在执行中或开始执行的时候是不能取消的
# time.sleep(3)
# print(task1.done())

# result 是阻塞的方法可以获取task的执行结果
print(task1.result())

# ---------

urls = [3,2,4]
all_task = [executor.submit(get_html, (url)) for url in urls]   # 批量提交

wait(all_task, return_when=FIRST_COMPLETED)
print("main")

# 要获取已经成功的task的返回
# for future in as_completed(all_task):
#     data = future.result()
#     print("get {} page".format(data))

# 通过executor的map获取已经完成的task的值
# for data in executor.map(get_html, urls):
#     print("get {} page".format(data)) # 跟提交值顺序相同

# ----
False
get page 2 success
get page 3 success
3
get page 2 success
main
get page 3 success
get page 4 success

from concurrent.futures import Future
#未来对象，task的返回容器

11.6 多进程编程-multiprocessing

# 多进程编程
# 耗cpu的操作，用多进程编程， 对于io操作来说， 使用多线程编程，进程切换代价要高于线程

# 1. 对于耗费cpu的操作，多进程由于多线程

import time
from concurrent.futures import ThreadPoolExecutor, as_completed
from concurrent.futures import ProcessPoolExecutor

def fib(n):
    if n<=2:
        return 1
    return fib(n-1)+fib(n-2)

if __name__ == "__main__":
    with ProcessPoolExecutor(3) as executor:  #last time is: 14.505059242248535
#     with ThreadPoolExecutor(3) as executor:  # last time is: 30.066641330718994
        all_task = [executor.submit(fib, (num)) for num in range(25,40)]
        start_time = time.time()
        for future in as_completed(all_task):
            data = future.result()
            print("exe result: {}".format(data))

        print("last time is: {}".format(time.time()-start_time))

#2. 对于io操作来说，多线程优于多进程
def random_sleep(n):
    time.sleep(n)
    return n

if __name__ == "__main__":
    # with ThreadPoolExecutor(3) as executor:
    with ProcessPoolExecutor(3) as executor:
        all_task = [executor.submit(random_sleep, (num)) for num in [1]*30]
        start_time = time.time()
        for future in as_completed(all_task):
            data = future.result()
            print("exe result: {}".format(data))

        print("last time is: {}".format(time.time()-start_time))

import os
import time
# fork只能用Linux/unix中
pid = os.fork()
print("lewen",pid)

if pid ==0:   #子进程拷贝
    print("子进程 %s，父进程 %s"%(os.getpid(),os.getppid()))
else:
    print("我是父进程：%s"%(pid))

time.sleep(2)

[root@doit ~]# python fork_test.py
('lewen', 16077)
我是父进程：16077
('lewen', 0)
子进程 16077，父进程 16076

import os
import time
# fork只能用Linux/unix中
print("lewen",pid)

pid = os.fork()

if pid ==0:   #子进程拷贝
    print("子进程 %s，父进程 %s"%(os.getpid(),os.getppid()))
else:
    print("我是父进程：%s"%(pid))

time.sleep(2)

[root@doit ~]# python fork_test.py
lewen
我是父进程：16096
子进程 16096，父进程 16095

os.fork()

from concurrent.futures import ProcessPoolExecutor  # 进程池，基于multiprocessing，推荐
import multiprocessing

# 多进程编程
import time

def get_html(n):
    time.sleep(n)
    print("sub_progress success")
    return n

class MyProcess(multiprocessing.Process):
    def run(self):
        pass

if __name__ == "__main__":
    # progress = multiprocessing.Process(target=get_html, args=(2,))
    # print(progress.pid)
    # progress.start()
    # print(progress.pid)
    # progress.join()
    # print("main progress end")

    """
    None
    10796
    sub_progress success
    main progress end

    """

    # 使用线程池
    pool = multiprocessing.Pool(multiprocessing.cpu_count())
    # result = pool.apply_async(get_html, args=(3,))  # 异步提交任务
    #
    # # 等待所有任务完成
    # pool.close()  # 关闭，不再接受新的任务进来，才不会出错
    # pool.join()
    #
    # print(result.get())
    """
    sub_progress success
    3
    """

    # imap
    # for result in pool.imap(get_html, [1, 5, 3]):
    #     print("{} sleep success".format(result))
    """
    sub_progress success
    1 sleep success
    sub_progress success
    sub_progress success
    5 sleep success
    3 sleep success
    """

    for result in pool.imap_unordered(get_html, [1, 5, 3]):  # 谁先完成就打出来
        print("{} sleep success".format(result))

    """
    sub_progress success
    1 sleep success
    sub_progress success
    3 sleep success
    sub_progress success
    5 sleep success

    """

11.7 进程间通信

1 multiprocessing.Queue

# 共享全局变量通信
# 共享全局变量不能适用于多进程编程，可以适用于多线程

def producer(a):
    a += 100
    time.sleep(2)

def consumer(a):
    time.sleep(2)
    print(a)

if __name__ == "__main__":
    a = 1
    my_producer = Process(target=producer, args=(a,))
    my_consumer = Process(target=consumer, args=(a,))
    my_producer.start()
    my_consumer.start()
    my_producer.join()
    my_consumer.join()
---
1

共享全局变量不能适用于多进程编程，可以适用于多线程

# multiprocessing中的queue不能用于pool进程池
# pool中的进程间通信需要使用manager中的queue
import time
from multiprocessing import Process, Queue, Pool, Manager, Pipe

def producer(queue):
    queue.put("a")
    time.sleep(2)

def consumer(queue):
    time.sleep(2)
    data = queue.get()
    print(data)

if __name__ == "__main__":
    queue = Manager().Queue(10)
    pool = Pool(2)

    pool.apply_async(producer, args=(queue,))
    pool.apply_async(consumer, args=(queue,))

    pool.close()
    pool.join()

--
a

2 pool中的进程间通信需要使用manager中的queue

#通过pipe(管道)实现进程间通信
#pipe的性能高于queue

def producer(pipe):
    pipe.send("lewen")

def consumer(pipe):
    print(pipe.recv())

if __name__ == "__main__":
    recevie_pipe, send_pipe = Pipe()
    # pipe只能适用于两个进程
    my_producer= Process(target=producer, args=(send_pipe, ))
    my_consumer = Process(target=consumer, args=(recevie_pipe,))

    my_producer.start()
    my_consumer.start()
    my_producer.join()
    my_consumer.join()

3 通过pipe(管道)实现进程间通信

内存共享

def add_data(p_dict, key, value):
    p_dict[key] = value

if __name__ == "__main__":
    progress_dict = Manager().dict()
    from queue import PriorityQueue  # 优先级队列，后插入的数据尽快被获取到

    first_progress = Process(target=add_data, args=(progress_dict, "lewen1", 22))
    second_progress = Process(target=add_data, args=(progress_dict, "lewen2", 23))

    first_progress.start()
    second_progress.start()
    first_progress.join()
    second_progress.join()

    print(progress_dict)

---
{'lewen1': 22, 'lewen2': 23}