Python 并行线程

Question

这里的代码下载了 3 个文件，并用它做了一些事情。但是在启动 Thread2 之前，它会等到 Thread1 完成。怎么让他们一起跑？指定一些带有注释的示例。谢谢

import threading
import urllib.request


def testForThread1():
    print('[Thread1]::Started')
    resp = urllib.request.urlopen('http://192.168.85.16/SOME_FILE')
    data = resp.read()
    # Do something with it
    return 'ok'


def testForThread2():
    print('[Thread2]::Started')
    resp = urllib.request.urlopen('http://192.168.85.10/SOME_FILE')
    data = resp.read()
    # Do something with it
    return 'ok'


if __name__ == "__main__":
    t1 = threading.Thread(name="Hello1", target=testForThread1())
    t1.start()
    t2 = threading.Thread(name="Hello2", target=testForThread2())
    t2.start()
    print(threading.enumerate())
    t1.join()
    t2.join()
    exit(0)

Answer 1

您正在执行线程实例创建中线程的目标函数。

if __name__ == "__main__":
    t1 = threading.Thread(name="Hello1", target=testForThread1()) # <<-- here
    t1.start()

这相当于:

if __name__ == "__main__":
    result = testForThread1() # == 'ok', this is the blocking execution
    t1 = threading.Thread(name="Hello1", target=result) 
    t1.start()

Thread.start() 的工作是执行该函数并将其结果存储在某个地方供您回收。如您所见，以前的格式是在主线程中执行阻塞函数，阻止您进行并行化(例如，它必须在到达调用第二个函数的行之前完成该函数执行)。

以非阻塞方式设置线程的正确方法是:

if __name__ == "__main__":
    t1 = threading.Thread(name="Hello1", target=testForThread1) # tell thread what the target function is
    # notice no function call braces for the function "testForThread1"
    t1.start() # tell the thread to execute the target function