import asyncio
import requests
import time
async def result(url):
# await request_url(url) # 第一条语句
# res = await request_url(url) # 第二条语句
await request_url1(url) # 第三条语句
print(f'-----{url}')
# print(url, res)
async def request_url(url):
res = requests.get(url)
print(url)
await asyncio.sleep(2)
print("execute_time:", time.time() - start)
return res
async def request_url1(url):
res=requests.get(url)
print(url)
time.sleep(2)
print('execute_time:',time.time()-start)
return res
url_list = ["https://www.csdn.net/",
"https://blog.csdn.net/qq_43380180/article/details/111573642",
"https://www.baidu.com/",
]
start = time.time()
print(f"start_time:{start}\n")
task = [result(url) for url in url_list]
loop = asyncio.get_event_loop()
loop.run_until_complete(asyncio.wait(task))
endtime = time.time() - start
print("\nendtime:", time.time())
print("all_execute_time:", endtime)
测试了代码中注释有“第一条语句”、“第二条语句”和“第三条语句”的语句发挥的作用，测试时取消测试语句的注释，其他两条语句被注释掉。首先，第一条语句和第二条语句的效果一样，在理清await的作用前我总有种幻想，是result会不管request_url的执行过程，发布个request_url任务直接向下执行，而结果和幻想结果不一致，我猜测是因为有返回值，解释器需要等待返回值的赋值，故第一条语句相比第二条语句去掉了返回值，测试结果仍没变化，经过思考，明白了这是协程，异步的进程或线程才会有我幻想的结果。只有第三条语句被执行时，程序的三个事件顺序执行，休眠两秒的动作会被执行三次。在执行第二条语句时，该程序的含义是发布三项访问url的并行执行的任务，每个任务并列地睡眠两秒。
展示执行不同语句的打印结果，第一条语句和第二条语句结果一样，所以只展示执行第二条语句的实验二和执行第三条语句的实验三：
实验二
start_time:1673699240.3729575 C:\Users\tellw\test\test1.py:35: DeprecationWarning: There is no current event loop loop = asyncio.get_event_loop() https://blog.csdn.net/qq_43380180/article/details/111573642 https://www.csdn.net/ https://www.baidu.com/ execute_time: 2.302398920059204 -----https://blog.csdn.net/qq_43380180/article/details/111573642 execute_time: 2.583828926086426 -----https://www.csdn.net/ execute_time: 2.709165573120117 -----https://www.baidu.com/ endtime: 1673699243.0838816 all_execute_time: 2.7109241485595703
start_time:1673699223.1047676 C:\Users\tellw\test\test1.py:35: DeprecationWarning: There is no current event loop loop = asyncio.get_event_loop() https://blog.csdn.net/qq_43380180/article/details/111573642 execute_time: 2.3865320682525635 -----https://blog.csdn.net/qq_43380180/article/details/111573642 https://www.csdn.net/ execute_time: 4.672637462615967 -----https://www.csdn.net/ https://www.baidu.com/ execute_time: 6.810583829879761 -----https://www.baidu.com/ endtime: 1673699229.9167387 all_execute_time: 6.811971187591553
对于异步线程的讨论：
import threading
import time
print(time.ctime())
def func(name,sec):
time.sleep(sec)
print(name,time.ctime())
t1=threading.Thread(target=func,args=('1',1))
t2=threading.Thread(target=func,args=('2',2))
t1.start()
t2.start()
# t1.join()
# t2.join()
print('main end',time.ctime())
上述代码执行结果Sat Jan 14 20:17:53 2023 main end Sat Jan 14 20:17:53 2023 1 Sat Jan 14 20:17:54 2023 2 Sat Jan 14 20:17:55 2023子线程睡1秒，子线程睡2秒，两个子线程睡两秒，主线程不睡，对应主线程调起其他子线程后自己忙自己的事的幻想，按理说主线程执行完后仍会等待其他子线程完成工作
Sat Jan 14 20:18:21 2023 1 Sat Jan 14 20:18:22 2023 2 Sat Jan 14 20:18:23 2023 main end Sat Jan 14 20:18:23 2023
参考链接：Python 异步 async/await（进阶详解）
Python threading实现多线程 基础篇