并发编程：异步+回调机制

一：进程

1、导入模块

   2.定义访问下载函数

   3.解析下载的内容

  4.在进程池里放任务，并把任务提交给get函数

 完整代码：

from concurrent.futures import ProcessPoolExecutor,ThreadPoolExecutor
import requests
import os
import time
import random

def get(url):
    print('%s GET %s' %(os.getpid(),url))   
    response=requests.get(url)               
    if response.status_code == 200:          
        return response.text                

def pasrse(obj):     
    res=obj.result()  
    print('%s 解析结果为：%s' %(os.getpid(),len(res)))

if __name__ == '__main__':
    urls=[
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.python.org',
    ]

    pool=ProcessPoolExecutor(4)     
    for url in urls:                
        obj=pool.submit(get,url)
        obj.add_done_callback(pasrse)  
    print('主进程',os.getpid())

运行结果：

主进程 5588
6976 GET https://www.baidu.com
17844 GET https://www.baidu.com
16832 GET https://www.baidu.com
8956 GET https://www.baidu.com
17844 GET https://www.baidu.com
5588 解析结果为：2443
8956 GET https://www.baidu.com
5588 解析结果为：2443
16832 GET https://www.baidu.com
5588 解析结果为：2443
6976 GET https://www.baidu.com
5588 解析结果为：2443
17844 GET https://www.python.org
5588 解析结果为：2443
5588 解析结果为：2443
5588 解析结果为：2443
5588 解析结果为：2443
5588 解析结果为：48887

Process finished with exit code 0

二：线程

过程与进程相似，但线程没有主次之分，哪个线程闲着了就由哪个线程干回调的活

from concurrent.futures import ProcessPoolExecutor,ThreadPoolExecutor
from threading import current_thread
import requests
import os
import time
import random

def get(url):
    print('%s GET %s' %(current_thread().name,url))
    response=requests.get(url)
    time.sleep(random.randint(1,3))

    if response.status_code == 200:
        return response.text

def pasrse(obj):
    res=obj.result()
    print('%s 解析结果为：%s' %(current_thread().name,len(res)))

if __name__ == '__main__':
    urls=[
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.baidu.com',
        'https://www.python.org',
    ]

    pool=ThreadPoolExecutor(4)
    for url in urls:
        obj=pool.submit(get,url)
        obj.add_done_callback(pasrse)

运行结果：

ThreadPoolExecutor-0_0 GET https://www.baidu.com
ThreadPoolExecutor-0_1 GET https://www.baidu.com
ThreadPoolExecutor-0_2 GET https://www.baidu.com
ThreadPoolExecutor-0_3 GET https://www.baidu.com
ThreadPoolExecutor-0_0 解析结果为：2443
ThreadPoolExecutor-0_0 GET https://www.baidu.com
ThreadPoolExecutor-0_2 解析结果为：2443
ThreadPoolExecutor-0_2 GET https://www.baidu.com
ThreadPoolExecutor-0_1 解析结果为：2443
ThreadPoolExecutor-0_1 GET https://www.baidu.com
ThreadPoolExecutor-0_0 解析结果为：2443
ThreadPoolExecutor-0_0 GET https://www.baidu.com
ThreadPoolExecutor-0_3 解析结果为：2443
ThreadPoolExecutor-0_3 GET https://www.python.org
ThreadPoolExecutor-0_2 解析结果为：2443
ThreadPoolExecutor-0_0 解析结果为：2443
ThreadPoolExecutor-0_1 解析结果为：2443
ThreadPoolExecutor-0_3 解析结果为：48887

Process finished with exit code 0