进程、线程之join方法

def join(self,timeout=None)

　　"""Wait until the thread terminates """

　　This blocks the calling thread until the thread whose join() method is called terminates  -- either normally or through an unhandled

      exception or until the optional timeout occurs.

　　这将阻止调用进程直到调用join()方法的进程终止--正常 或者 抛出一个非处理的异常 或者 直到 可选 的参数 timeout发生.

　　When the timeout argument is present and not None, it should be a floating point number specifying a timeout for the operation in seconds (or fractions                     thereof). As join() always returns None, you must call isAlive() after join() to decide whether a timeout happened -- if the thread is still alive, the join() call                 timeout.

　　当timeout参数存在且不是None时，它应该是一个浮点数指明操作的超时时间(以秒为单位)。 join()方法总是返回None,你必须在调用 join(） 方法之后 调用  isAlive()方法 决定超时是否发生--如果线程仍处于活动状态，说明 join(）调用超时。

 

　　When the timeout argument is not present or None, the operation will block until the thread terminates.

　　A thread can be join()ed many times.

　　join() raises a RuntimeError if an attempt is made to join the cureent thread as that would cause a deadblock.

　　It is also an error to join() a thread  before it has been started and attempts to do so raises the same exception.

　　如果尝试 join 当前线程，join()方法会抛出 运行时错误异常 ，因为那样会导致死锁。 在一个线程开始调用start()方法之前，调用join()方法，也会抛出同样的异常。

 

 

import time
from threading import Timer,Thread

def func():
    print(time.strftime("%Y-%m-%d %H:%M:%S"))
    # timer.join() # RuntimeError: cannot join current thread 如果尝试加入当前线程 join()方法，会抛出运行时错误 异常，因为这会导致死锁
    print("执行我啦")

if __name__ == '__main__':
    print(time.strftime("%Y-%m-%d %H:%M:%S"))
    timer = Timer(1,func)  # 当创建线程后，延时1秒后执行
    # timer.join()   # RuntimeError: cannot join thread before it is started  在线程创建启动之前，运行join()方法，抛出 运行时错误 异常
    timer.start()  # 创建线程，并执行线程
    timer.join()
    print(time.strftime("%Y-%m-%d %H:%M:%S"))